Merge remote-tracking branch 'remotes/berrange/tags/docs-pull-request' into staging

docs: add docs about use of automatic cleanup functions

This is ostensibly about adding docs for the g_autofree/g_autoptr
macros. As part of doing that, however, the existing HACKING doc
is merged into the CODING_STYLE doc and the text is converted to
rst with a table of contents.

# gpg: Signature made Thu 05 Sep 2019 14:43:44 BST
# gpg:                using RSA key DAF3A6FDB26B62912D0E8E3FBE86EBB415104FDF
# gpg: Good signature from "Daniel P. Berrange <dan@berrange.com>" [full]
# gpg:                 aka "Daniel P. Berrange <berrange@redhat.com>" [full]
# Primary key fingerprint: DAF3 A6FD B26B 6291 2D0E  8E3F BE86 EBB4 1510 4FDF

* remotes/berrange/tags/docs-pull-request:
  docs: split the CODING_STYLE doc into distinct groups
  docs: document use of automatic cleanup functions in glib
  docs: merge HACKING.rst contents into CODING_STYLE.rst
  docs: convert README, CODING_STYLE and HACKING to RST syntax

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

5 files changed, 671 insertions, 492 deletions

diff --git a/CODING_STYLE b/CODING_STYLE
deleted file mode 100644
index cb8edcbb36..0000000000
--- a/CODING_STYLE
+++ /dev/null
@@ -1,216 +0,0 @@
-QEMU Coding Style
-=================
-
-Please use the script checkpatch.pl in the scripts directory to check
-patches before submitting.
-
-1. Whitespace
-
-Of course, the most important aspect in any coding style is whitespace.
-Crusty old coders who have trouble spotting the glasses on their noses
-can tell the difference between a tab and eight spaces from a distance
-of approximately fifteen parsecs.  Many a flamewar has been fought and
-lost on this issue.
-
-QEMU indents are four spaces.  Tabs are never used, except in Makefiles
-where they have been irreversibly coded into the syntax.
-Spaces of course are superior to tabs because:
-
- - You have just one way to specify whitespace, not two.  Ambiguity breeds
-   mistakes.
- - The confusion surrounding 'use tabs to indent, spaces to justify' is gone.
- - Tab indents push your code to the right, making your screen seriously
-   unbalanced.
- - Tabs will be rendered incorrectly on editors who are misconfigured not
-   to use tab stops of eight positions.
- - Tabs are rendered badly in patches, causing off-by-one errors in almost
-   every line.
- - It is the QEMU coding style.
-
-Do not leave whitespace dangling off the ends of lines.
-
-1.1 Multiline Indent
-
-There are several places where indent is necessary:
-
- - if/else
- - while/for
- - function definition & call
-
-When breaking up a long line to fit within line width, we need a proper indent
-for the following lines.
-
-In case of if/else, while/for, align the secondary lines just after the
-opening parenthesis of the first.
-
-For example:
-
-    if (a == 1 &&
-        b == 2) {
-
-    while (a == 1 &&
-           b == 2) {
-
-In case of function, there are several variants:
-
-    * 4 spaces indent from the beginning
-    * align the secondary lines just after the opening parenthesis of the
-      first
-
-For example:
-
-    do_something(x, y,
-        z);
-
-    do_something(x, y,
-                 z);
-
-    do_something(x, do_another(y,
-                               z));
-
-2. Line width
-
-Lines should be 80 characters; try not to make them longer.
-
-Sometimes it is hard to do, especially when dealing with QEMU subsystems
-that use long function or symbol names.  Even in that case, do not make
-lines much longer than 80 characters.
-
-Rationale:
- - Some people like to tile their 24" screens with a 6x4 matrix of 80x24
-   xterms and use vi in all of them.  The best way to punish them is to
-   let them keep doing it.
- - Code and especially patches is much more readable if limited to a sane
-   line length.  Eighty is traditional.
- - The four-space indentation makes the most common excuse ("But look
-   at all that white space on the left!") moot.
- - It is the QEMU coding style.
-
-3. Naming
-
-Variables are lower_case_with_underscores; easy to type and read.  Structured
-type names are in CamelCase; harder to type but standing out.  Enum type
-names and function type names should also be in CamelCase.  Scalar type
-names are lower_case_with_underscores_ending_with_a_t, like the POSIX
-uint64_t and family.  Note that this last convention contradicts POSIX
-and is therefore likely to be changed.
-
-When wrapping standard library functions, use the prefix qemu_ to alert
-readers that they are seeing a wrapped version; otherwise avoid this prefix.
-
-4. Block structure
-
-Every indented statement is braced; even if the block contains just one
-statement.  The opening brace is on the line that contains the control
-flow statement that introduces the new block; the closing brace is on the
-same line as the else keyword, or on a line by itself if there is no else
-keyword.  Example:
-
-    if (a == 5) {
-        printf("a was 5.\n");
-    } else if (a == 6) {
-        printf("a was 6.\n");
-    } else {
-        printf("a was something else entirely.\n");
-    }
-
-Note that 'else if' is considered a single statement; otherwise a long if/
-else if/else if/.../else sequence would need an indent for every else
-statement.
-
-An exception is the opening brace for a function; for reasons of tradition
-and clarity it comes on a line by itself:
-
-    void a_function(void)
-    {
-        do_something();
-    }
-
-Rationale: a consistent (except for functions...) bracing style reduces
-ambiguity and avoids needless churn when lines are added or removed.
-Furthermore, it is the QEMU coding style.
-
-5. Declarations
-
-Mixed declarations (interleaving statements and declarations within
-blocks) are generally not allowed; declarations should be at the beginning
-of blocks.
-
-Every now and then, an exception is made for declarations inside a
-#ifdef or #ifndef block: if the code looks nicer, such declarations can
-be placed at the top of the block even if there are statements above.
-On the other hand, however, it's often best to move that #ifdef/#ifndef
-block to a separate function altogether.
-
-6. Conditional statements
-
-When comparing a variable for (in)equality with a constant, list the
-constant on the right, as in:
-
-    if (a == 1) {
-        /* Reads like: "If a equals 1" */
-        do_something();
-    }
-
-Rationale: Yoda conditions (as in 'if (1 == a)') are awkward to read.
-Besides, good compilers already warn users when '==' is mis-typed as '=',
-even when the constant is on the right.
-
-7. Comment style
-
-We use traditional C-style /* */ comments and avoid // comments.
-
-Rationale: The // form is valid in C99, so this is purely a matter of
-consistency of style. The checkpatch script will warn you about this.
-
-Multiline comment blocks should have a row of stars on the left,
-and the initial /* and terminating */ both on their own lines:
-    /*
-     * like
-     * this
-     */
-This is the same format required by the Linux kernel coding style.
-
-(Some of the existing comments in the codebase use the GNU Coding
-Standards form which does not have stars on the left, or other
-variations; avoid these when writing new comments, but don't worry
-about converting to the preferred form unless you're editing that
-comment anyway.)
-
-Rationale: Consistency, and ease of visually picking out a multiline
-comment from the surrounding code.
-
-8. trace-events style
-
-8.1 0x prefix
-
-In trace-events files, use a '0x' prefix to specify hex numbers, as in:
-
-some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
-
-An exception is made for groups of numbers that are hexadecimal by
-convention and separated by the symbols '.', '/', ':', or ' ' (such as
-PCI bus id):
-
-another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
-
-However, you can use '0x' for such groups if you want. Anyway, be sure that
-it is obvious that numbers are in hex, ex.:
-
-data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
-
-Rationale: hex numbers are hard to read in logs when there is no 0x prefix,
-especially when (occasionally) the representation doesn't contain any letters
-and especially in one line with other decimal numbers. Number groups are allowed
-to not use '0x' because for some things notations like %x.%x.%x are used not
-only in Qemu. Also dumping raw data bytes with '0x' is less readable.
-
-8.2 '#' printf flag
-
-Do not use printf flag '#', like '%#x'.
-
-Rationale: there are two ways to add a '0x' prefix to printed number: '0x%...'
-and '%#...'. For consistency the only one way should be used. Arguments for
-'0x%' are:
- - it is more popular
- - '%#' omits the 0x for the value 0 which makes output inconsistent
diff --git a/CODING_STYLE.rst b/CODING_STYLE.rst
new file mode 100644
index 0000000000..427699e0e4
--- /dev/null
+++ b/CODING_STYLE.rst
@@ -0,0 +1,641 @@
+=================
+QEMU Coding Style
+=================
+
+.. contents:: Table of Contents
+
+Please use the script checkpatch.pl in the scripts directory to check
+patches before submitting.
+
+Formatting and style
+********************
+
+Whitespace
+==========
+
+Of course, the most important aspect in any coding style is whitespace.
+Crusty old coders who have trouble spotting the glasses on their noses
+can tell the difference between a tab and eight spaces from a distance
+of approximately fifteen parsecs.  Many a flamewar has been fought and
+lost on this issue.
+
+QEMU indents are four spaces.  Tabs are never used, except in Makefiles
+where they have been irreversibly coded into the syntax.
+Spaces of course are superior to tabs because:
+
+* You have just one way to specify whitespace, not two.  Ambiguity breeds
+  mistakes.
+* The confusion surrounding 'use tabs to indent, spaces to justify' is gone.
+* Tab indents push your code to the right, making your screen seriously
+  unbalanced.
+* Tabs will be rendered incorrectly on editors who are misconfigured not
+  to use tab stops of eight positions.
+* Tabs are rendered badly in patches, causing off-by-one errors in almost
+  every line.
+* It is the QEMU coding style.
+
+Do not leave whitespace dangling off the ends of lines.
+
+Multiline Indent
+----------------
+
+There are several places where indent is necessary:
+
+* if/else
+* while/for
+* function definition & call
+
+When breaking up a long line to fit within line width, we need a proper indent
+for the following lines.
+
+In case of if/else, while/for, align the secondary lines just after the
+opening parenthesis of the first.
+
+For example:
+
+.. code-block:: c
+
+    if (a == 1 &&
+        b == 2) {
+
+    while (a == 1 &&
+           b == 2) {
+
+In case of function, there are several variants:
+
+* 4 spaces indent from the beginning
+* align the secondary lines just after the opening parenthesis of the first
+
+For example:
+
+.. code-block:: c
+
+    do_something(x, y,
+        z);
+
+    do_something(x, y,
+                 z);
+
+    do_something(x, do_another(y,
+                               z));
+
+Line width
+==========
+
+Lines should be 80 characters; try not to make them longer.
+
+Sometimes it is hard to do, especially when dealing with QEMU subsystems
+that use long function or symbol names.  Even in that case, do not make
+lines much longer than 80 characters.
+
+Rationale:
+
+* Some people like to tile their 24" screens with a 6x4 matrix of 80x24
+  xterms and use vi in all of them.  The best way to punish them is to
+  let them keep doing it.
+* Code and especially patches is much more readable if limited to a sane
+  line length.  Eighty is traditional.
+* The four-space indentation makes the most common excuse ("But look
+  at all that white space on the left!") moot.
+* It is the QEMU coding style.
+
+Naming
+======
+
+Variables are lower_case_with_underscores; easy to type and read.  Structured
+type names are in CamelCase; harder to type but standing out.  Enum type
+names and function type names should also be in CamelCase.  Scalar type
+names are lower_case_with_underscores_ending_with_a_t, like the POSIX
+uint64_t and family.  Note that this last convention contradicts POSIX
+and is therefore likely to be changed.
+
+When wrapping standard library functions, use the prefix ``qemu_`` to alert
+readers that they are seeing a wrapped version; otherwise avoid this prefix.
+
+Block structure
+===============
+
+Every indented statement is braced; even if the block contains just one
+statement.  The opening brace is on the line that contains the control
+flow statement that introduces the new block; the closing brace is on the
+same line as the else keyword, or on a line by itself if there is no else
+keyword.  Example:
+
+.. code-block:: c
+
+    if (a == 5) {
+        printf("a was 5.\n");
+    } else if (a == 6) {
+        printf("a was 6.\n");
+    } else {
+        printf("a was something else entirely.\n");
+    }
+
+Note that 'else if' is considered a single statement; otherwise a long if/
+else if/else if/.../else sequence would need an indent for every else
+statement.
+
+An exception is the opening brace for a function; for reasons of tradition
+and clarity it comes on a line by itself:
+
+.. code-block:: c
+
+    void a_function(void)
+    {
+        do_something();
+    }
+
+Rationale: a consistent (except for functions...) bracing style reduces
+ambiguity and avoids needless churn when lines are added or removed.
+Furthermore, it is the QEMU coding style.
+
+Declarations
+============
+
+Mixed declarations (interleaving statements and declarations within
+blocks) are generally not allowed; declarations should be at the beginning
+of blocks.
+
+Every now and then, an exception is made for declarations inside a
+#ifdef or #ifndef block: if the code looks nicer, such declarations can
+be placed at the top of the block even if there are statements above.
+On the other hand, however, it's often best to move that #ifdef/#ifndef
+block to a separate function altogether.
+
+Conditional statements
+======================
+
+When comparing a variable for (in)equality with a constant, list the
+constant on the right, as in:
+
+.. code-block:: c
+
+    if (a == 1) {
+        /* Reads like: "If a equals 1" */
+        do_something();
+    }
+
+Rationale: Yoda conditions (as in 'if (1 == a)') are awkward to read.
+Besides, good compilers already warn users when '==' is mis-typed as '=',
+even when the constant is on the right.
+
+Comment style
+=============
+
+We use traditional C-style /``*`` ``*``/ comments and avoid // comments.
+
+Rationale: The // form is valid in C99, so this is purely a matter of
+consistency of style. The checkpatch script will warn you about this.
+
+Multiline comment blocks should have a row of stars on the left,
+and the initial /``*`` and terminating ``*``/ both on their own lines:
+
+.. code-block:: c
+
+    /*
+     * like
+     * this
+     */
+
+This is the same format required by the Linux kernel coding style.
+
+(Some of the existing comments in the codebase use the GNU Coding
+Standards form which does not have stars on the left, or other
+variations; avoid these when writing new comments, but don't worry
+about converting to the preferred form unless you're editing that
+comment anyway.)
+
+Rationale: Consistency, and ease of visually picking out a multiline
+comment from the surrounding code.
+
+Language usage
+**************
+
+Preprocessor
+============
+
+Variadic macros
+---------------
+
+For variadic macros, stick with this C99-like syntax:
+
+.. code-block:: c
+
+    #define DPRINTF(fmt, ...)                                       \
+        do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
+
+Include directives
+------------------
+
+Order include directives as follows:
+
+.. code-block:: c
+
+    #include "qemu/osdep.h"  /* Always first... */
+    #include <...>           /* then system headers... */
+    #include "..."           /* and finally QEMU headers. */
+
+The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
+of core system headers like <stdint.h>.  It must be the first include so that
+core system headers included by external libraries get the preprocessor macros
+that QEMU depends on.
+
+Do not include "qemu/osdep.h" from header files since the .c file will have
+already included it.
+
+C types
+=======
+
+It should be common sense to use the right type, but we have collected
+a few useful guidelines here.
+
+Scalars
+-------
+
+If you're using "int" or "long", odds are good that there's a better type.
+If a variable is counting something, it should be declared with an
+unsigned type.
+
+If it's host memory-size related, size_t should be a good choice (use
+ssize_t only if required). Guest RAM memory offsets must use ram_addr_t,
+but only for RAM, it may not cover whole guest address space.
+
+If it's file-size related, use off_t.
+If it's file-offset related (i.e., signed), use off_t.
+If it's just counting small numbers use "unsigned int";
+(on all but oddball embedded systems, you can assume that that
+type is at least four bytes wide).
+
+In the event that you require a specific width, use a standard type
+like int32_t, uint32_t, uint64_t, etc.  The specific types are
+mandatory for VMState fields.
+
+Don't use Linux kernel internal types like u32, __u32 or __le32.
+
+Use hwaddr for guest physical addresses except pcibus_t
+for PCI addresses.  In addition, ram_addr_t is a QEMU internal address
+space that maps guest RAM physical addresses into an intermediate
+address space that can map to host virtual address spaces.  Generally
+speaking, the size of guest memory can always fit into ram_addr_t but
+it would not be correct to store an actual guest physical address in a
+ram_addr_t.
+
+For CPU virtual addresses there are several possible types.
+vaddr is the best type to use to hold a CPU virtual address in
+target-independent code. It is guaranteed to be large enough to hold a
+virtual address for any target, and it does not change size from target
+to target. It is always unsigned.
+target_ulong is a type the size of a virtual address on the CPU; this means
+it may be 32 or 64 bits depending on which target is being built. It should
+therefore be used only in target-specific code, and in some
+performance-critical built-per-target core code such as the TLB code.
+There is also a signed version, target_long.
+abi_ulong is for the ``*``-user targets, and represents a type the size of
+'void ``*``' in that target's ABI. (This may not be the same as the size of a
+full CPU virtual address in the case of target ABIs which use 32 bit pointers
+on 64 bit CPUs, like sparc32plus.) Definitions of structures that must match
+the target's ABI must use this type for anything that on the target is defined
+to be an 'unsigned long' or a pointer type.
+There is also a signed version, abi_long.
+
+Of course, take all of the above with a grain of salt.  If you're about
+to use some system interface that requires a type like size_t, pid_t or
+off_t, use matching types for any corresponding variables.
+
+Also, if you try to use e.g., "unsigned int" as a type, and that
+conflicts with the signedness of a related variable, sometimes
+it's best just to use the *wrong* type, if "pulling the thread"
+and fixing all related variables would be too invasive.
+
+Finally, while using descriptive types is important, be careful not to
+go overboard.  If whatever you're doing causes warnings, or requires
+casts, then reconsider or ask for help.
+
+Pointers
+--------
+
+Ensure that all of your pointers are "const-correct".
+Unless a pointer is used to modify the pointed-to storage,
+give it the "const" attribute.  That way, the reader knows
+up-front that this is a read-only pointer.  Perhaps more
+importantly, if we're diligent about this, when you see a non-const
+pointer, you're guaranteed that it is used to modify the storage
+it points to, or it is aliased to another pointer that is.
+
+Typedefs
+--------
+
+Typedefs are used to eliminate the redundant 'struct' keyword, since type
+names have a different style than other identifiers ("CamelCase" versus
+"snake_case").  Each named struct type should have a CamelCase name and a
+corresponding typedef.
+
+Since certain C compilers choke on duplicated typedefs, you should avoid
+them and declare a typedef only in one header file.  For common types,
+you can use "include/qemu/typedefs.h" for example.  However, as a matter
+of convenience it is also perfectly fine to use forward struct
+definitions instead of typedefs in headers and function prototypes; this
+avoids problems with duplicated typedefs and reduces the need to include
+headers from other headers.
+
+Reserved namespaces in C and POSIX
+----------------------------------
+
+Underscore capital, double underscore, and underscore 't' suffixes should be
+avoided.
+
+Low level memory management
+===========================
+
+Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
+APIs is not allowed in the QEMU codebase. Instead of these routines,
+use the GLib memory allocation routines g_malloc/g_malloc0/g_new/
+g_new0/g_realloc/g_free or QEMU's qemu_memalign/qemu_blockalign/qemu_vfree
+APIs.
+
+Please note that g_malloc will exit on allocation failure, so there
+is no need to test for failure (as you would have to with malloc).
+Calling g_malloc with a zero size is valid and will return NULL.
+
+Prefer g_new(T, n) instead of g_malloc(sizeof(T) ``*`` n) for the following
+reasons:
+
+* It catches multiplication overflowing size_t;
+* It returns T ``*`` instead of void ``*``, letting compiler catch more type errors.
+
+Declarations like
+
+.. code-block:: c
+
+    T *v = g_malloc(sizeof(*v))
+
+are acceptable, though.
+
+Memory allocated by qemu_memalign or qemu_blockalign must be freed with
+qemu_vfree, since breaking this will cause problems on Win32.
+
+String manipulation
+===================
+
+Do not use the strncpy function.  As mentioned in the man page, it does *not*
+guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
+It also zeros trailing destination bytes out to the specified length.  Instead,
+use this similar function when possible, but note its different signature:
+
+.. code-block:: c
+
+    void pstrcpy(char *dest, int dest_buf_size, const char *src)
+
+Don't use strcat because it can't check for buffer overflows, but:
+
+.. code-block:: c
+
+    char *pstrcat(char *buf, int buf_size, const char *s)
+
+The same limitation exists with sprintf and vsprintf, so use snprintf and
+vsnprintf.
+
+QEMU provides other useful string functions:
+
+.. code-block:: c
+
+    int strstart(const char *str, const char *val, const char **ptr)
+    int stristart(const char *str, const char *val, const char **ptr)
+    int qemu_strnlen(const char *s, int max_len)
+
+There are also replacement character processing macros for isxyz and toxyz,
+so instead of e.g. isalnum you should use qemu_isalnum.
+
+Because of the memory management rules, you must use g_strdup/g_strndup
+instead of plain strdup/strndup.
+
+Printf-style functions
+======================
+
+Whenever you add a new printf-style function, i.e., one with a format
+string argument and following "..." in its prototype, be sure to use
+gcc's printf attribute directive in the prototype.
+
+This makes it so gcc's -Wformat and -Wformat-security options can do
+their jobs and cross-check format strings with the number and types
+of arguments.
+
+C standard, implementation defined and undefined behaviors
+==========================================================
+
+C code in QEMU should be written to the C99 language specification. A copy
+of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
+included, formatted as a draft, can be downloaded from:
+
+    `<http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf>`_
+
+The C language specification defines regions of undefined behavior and
+implementation defined behavior (to give compiler authors enough leeway to
+produce better code).  In general, code in QEMU should follow the language
+specification and avoid both undefined and implementation defined
+constructs. ("It works fine on the gcc I tested it with" is not a valid
+argument...) However there are a few areas where we allow ourselves to
+assume certain behaviors because in practice all the platforms we care about
+behave in the same way and writing strictly conformant code would be
+painful. These are:
+
+* you may assume that integers are 2s complement representation
+* you may assume that right shift of a signed integer duplicates
+  the sign bit (ie it is an arithmetic shift, not a logical shift)
+
+In addition, QEMU assumes that the compiler does not use the latitude
+given in C99 and C11 to treat aspects of signed '<<' as undefined, as
+documented in the GNU Compiler Collection manual starting at version 4.0.
+
+Automatic memory deallocation
+=============================
+
+QEMU has a mandatory dependency either the GCC or CLang compiler. As
+such it has the freedom to make use of a C language extension for
+automatically running a cleanup function when a stack variable goes
+out of scope. This can be used to simplify function cleanup paths,
+often allowing many goto jumps to be eliminated, through automatic
+free'ing of memory.
+
+The GLib2 library provides a number of functions/macros for enabling
+automatic cleanup:
+
+  `<https://developer.gnome.org/glib/stable/glib-Miscellaneous-Macros.html>`_
+
+Most notably:
+
+* g_autofree - will invoke g_free() on the variable going out of scope
+
+* g_autoptr - for structs / objects, will invoke the cleanup func created
+  by a previous use of G_DEFINE_AUTOPTR_CLEANUP_FUNC. This is
+  supported for most GLib data types and GObjects
+
+For example, instead of
+
+.. code-block:: c
+
+    int somefunc(void) {
+        int ret = -1;
+        char *foo = g_strdup_printf("foo%", "wibble");
+        GList *bar = .....
+
+        if (eek) {
+           goto cleanup;
+        }
+
+        ret = 0;
+
+      cleanup:
+        g_free(foo);
+        g_list_free(bar);
+        return ret;
+    }
+
+Using g_autofree/g_autoptr enables the code to be written as:
+
+.. code-block:: c
+
+    int somefunc(void) {
+        g_autofree char *foo = g_strdup_printf("foo%", "wibble");
+        g_autoptr (GList) bar = .....
+
+        if (eek) {
+           return -1;
+        }
+
+        return 0;
+    }
+
+While this generally results in simpler, less leak-prone code, there
+are still some caveats to beware of
+
+* Variables declared with g_auto* MUST always be initialized,
+  otherwise the cleanup function will use uninitialized stack memory
+
+* If a variable declared with g_auto* holds a value which must
+  live beyond the life of the function, that value must be saved
+  and the original variable NULL'd out. This can be simpler using
+  g_steal_pointer
+
+
+.. code-block:: c
+
+    char *somefunc(void) {
+        g_autofree char *foo = g_strdup_printf("foo%", "wibble");
+        g_autoptr (GList) bar = .....
+
+        if (eek) {
+           return NULL;
+        }
+
+        return g_steal_pointer(&foo);
+    }
+
+
+QEMU Specific Idioms
+********************
+
+Error handling and reporting
+============================
+
+Reporting errors to the human user
+----------------------------------
+
+Do not use printf(), fprintf() or monitor_printf().  Instead, use
+error_report() or error_vreport() from error-report.h.  This ensures the
+error is reported in the right place (current monitor or stderr), and in
+a uniform format.
+
+Use error_printf() & friends to print additional information.
+
+error_report() prints the current location.  In certain common cases
+like command line parsing, the current location is tracked
+automatically.  To manipulate it manually, use the loc_``*``() from
+error-report.h.
+
+Propagating errors
+------------------
+
+An error can't always be reported to the user right where it's detected,
+but often needs to be propagated up the call chain to a place that can
+handle it.  This can be done in various ways.
+
+The most flexible one is Error objects.  See error.h for usage
+information.
+
+Use the simplest suitable method to communicate success / failure to
+callers.  Stick to common methods: non-negative on success / -1 on
+error, non-negative / -errno, non-null / null, or Error objects.
+
+Example: when a function returns a non-null pointer on success, and it
+can fail only in one way (as far as the caller is concerned), returning
+null on failure is just fine, and certainly simpler and a lot easier on
+the eyes than propagating an Error object through an Error ``*````*`` parameter.
+
+Example: when a function's callers need to report details on failure
+only the function really knows, use Error ``*````*``, and set suitable errors.
+
+Do not report an error to the user when you're also returning an error
+for somebody else to handle.  Leave the reporting to the place that
+consumes the error returned.
+
+Handling errors
+---------------
+
+Calling exit() is fine when handling configuration errors during
+startup.  It's problematic during normal operation.  In particular,
+monitor commands should never exit().
+
+Do not call exit() or abort() to handle an error that can be triggered
+by the guest (e.g., some unimplemented corner case in guest code
+translation or device emulation).  Guests should not be able to
+terminate QEMU.
+
+Note that &error_fatal is just another way to exit(1), and &error_abort
+is just another way to abort().
+
+
+trace-events style
+==================
+
+0x prefix
+---------
+
+In trace-events files, use a '0x' prefix to specify hex numbers, as in:
+
+.. code-block::
+
+    some_trace(unsigned x, uint64_t y) "x 0x%x y 0x" PRIx64
+
+An exception is made for groups of numbers that are hexadecimal by
+convention and separated by the symbols '.', '/', ':', or ' ' (such as
+PCI bus id):
+
+.. code-block::
+
+    another_trace(int cssid, int ssid, int dev_num) "bus id: %x.%x.%04x"
+
+However, you can use '0x' for such groups if you want. Anyway, be sure that
+it is obvious that numbers are in hex, ex.:
+
+.. code-block::
+
+    data_dump(uint8_t c1, uint8_t c2, uint8_t c3) "bytes (in hex): %02x %02x %02x"
+
+Rationale: hex numbers are hard to read in logs when there is no 0x prefix,
+especially when (occasionally) the representation doesn't contain any letters
+and especially in one line with other decimal numbers. Number groups are allowed
+to not use '0x' because for some things notations like %x.%x.%x are used not
+only in Qemu. Also dumping raw data bytes with '0x' is less readable.
+
+'#' printf flag
+---------------
+
+Do not use printf flag '#', like '%#x'.
+
+Rationale: there are two ways to add a '0x' prefix to printed number: '0x%...'
+and '%#...'. For consistency the only one way should be used. Arguments for
+'0x%' are:
+
+* it is more popular
+* '%#' omits the 0x for the value 0 which makes output inconsistent
diff --git a/HACKING b/HACKING
deleted file mode 100644
index 097d482603..0000000000
--- a/HACKING
+++ /dev/null
@@ -1,257 +0,0 @@
-1. Preprocessor
-
-1.1. Variadic macros
-
-For variadic macros, stick with this C99-like syntax:
-
-#define DPRINTF(fmt, ...)                                       \
-    do { printf("IRQ: " fmt, ## __VA_ARGS__); } while (0)
-
-1.2. Include directives
-
-Order include directives as follows:
-
-#include "qemu/osdep.h"  /* Always first... */
-#include <...>           /* then system headers... */
-#include "..."           /* and finally QEMU headers. */
-
-The "qemu/osdep.h" header contains preprocessor macros that affect the behavior
-of core system headers like <stdint.h>.  It must be the first include so that
-core system headers included by external libraries get the preprocessor macros
-that QEMU depends on.
-
-Do not include "qemu/osdep.h" from header files since the .c file will have
-already included it.
-
-2. C types
-
-It should be common sense to use the right type, but we have collected
-a few useful guidelines here.
-
-2.1. Scalars
-
-If you're using "int" or "long", odds are good that there's a better type.
-If a variable is counting something, it should be declared with an
-unsigned type.
-
-If it's host memory-size related, size_t should be a good choice (use
-ssize_t only if required). Guest RAM memory offsets must use ram_addr_t,
-but only for RAM, it may not cover whole guest address space.
-
-If it's file-size related, use off_t.
-If it's file-offset related (i.e., signed), use off_t.
-If it's just counting small numbers use "unsigned int";
-(on all but oddball embedded systems, you can assume that that
-type is at least four bytes wide).
-
-In the event that you require a specific width, use a standard type
-like int32_t, uint32_t, uint64_t, etc.  The specific types are
-mandatory for VMState fields.
-
-Don't use Linux kernel internal types like u32, __u32 or __le32.
-
-Use hwaddr for guest physical addresses except pcibus_t
-for PCI addresses.  In addition, ram_addr_t is a QEMU internal address
-space that maps guest RAM physical addresses into an intermediate
-address space that can map to host virtual address spaces.  Generally
-speaking, the size of guest memory can always fit into ram_addr_t but
-it would not be correct to store an actual guest physical address in a
-ram_addr_t.
-
-For CPU virtual addresses there are several possible types.
-vaddr is the best type to use to hold a CPU virtual address in
-target-independent code. It is guaranteed to be large enough to hold a
-virtual address for any target, and it does not change size from target
-to target. It is always unsigned.
-target_ulong is a type the size of a virtual address on the CPU; this means
-it may be 32 or 64 bits depending on which target is being built. It should
-therefore be used only in target-specific code, and in some
-performance-critical built-per-target core code such as the TLB code.
-There is also a signed version, target_long.
-abi_ulong is for the *-user targets, and represents a type the size of
-'void *' in that target's ABI. (This may not be the same as the size of a
-full CPU virtual address in the case of target ABIs which use 32 bit pointers
-on 64 bit CPUs, like sparc32plus.) Definitions of structures that must match
-the target's ABI must use this type for anything that on the target is defined
-to be an 'unsigned long' or a pointer type.
-There is also a signed version, abi_long.
-
-Of course, take all of the above with a grain of salt.  If you're about
-to use some system interface that requires a type like size_t, pid_t or
-off_t, use matching types for any corresponding variables.
-
-Also, if you try to use e.g., "unsigned int" as a type, and that
-conflicts with the signedness of a related variable, sometimes
-it's best just to use the *wrong* type, if "pulling the thread"
-and fixing all related variables would be too invasive.
-
-Finally, while using descriptive types is important, be careful not to
-go overboard.  If whatever you're doing causes warnings, or requires
-casts, then reconsider or ask for help.
-
-2.2. Pointers
-
-Ensure that all of your pointers are "const-correct".
-Unless a pointer is used to modify the pointed-to storage,
-give it the "const" attribute.  That way, the reader knows
-up-front that this is a read-only pointer.  Perhaps more
-importantly, if we're diligent about this, when you see a non-const
-pointer, you're guaranteed that it is used to modify the storage
-it points to, or it is aliased to another pointer that is.
-
-2.3. Typedefs
-
-Typedefs are used to eliminate the redundant 'struct' keyword, since type
-names have a different style than other identifiers ("CamelCase" versus
-"snake_case").  Each named struct type should have a CamelCase name and a
-corresponding typedef.
-
-Since certain C compilers choke on duplicated typedefs, you should avoid
-them and declare a typedef only in one header file.  For common types,
-you can use "include/qemu/typedefs.h" for example.  However, as a matter
-of convenience it is also perfectly fine to use forward struct
-definitions instead of typedefs in headers and function prototypes; this
-avoids problems with duplicated typedefs and reduces the need to include
-headers from other headers.
-
-2.4. Reserved namespaces in C and POSIX
-Underscore capital, double underscore, and underscore 't' suffixes should be
-avoided.
-
-3. Low level memory management
-
-Use of the malloc/free/realloc/calloc/valloc/memalign/posix_memalign
-APIs is not allowed in the QEMU codebase. Instead of these routines,
-use the GLib memory allocation routines g_malloc/g_malloc0/g_new/
-g_new0/g_realloc/g_free or QEMU's qemu_memalign/qemu_blockalign/qemu_vfree
-APIs.
-
-Please note that g_malloc will exit on allocation failure, so there
-is no need to test for failure (as you would have to with malloc).
-Calling g_malloc with a zero size is valid and will return NULL.
-
-Prefer g_new(T, n) instead of g_malloc(sizeof(T) * n) for the following
-reasons:
-
-  a. It catches multiplication overflowing size_t;
-  b. It returns T * instead of void *, letting compiler catch more type
-     errors.
-
-Declarations like T *v = g_malloc(sizeof(*v)) are acceptable, though.
-
-Memory allocated by qemu_memalign or qemu_blockalign must be freed with
-qemu_vfree, since breaking this will cause problems on Win32.
-
-4. String manipulation
-
-Do not use the strncpy function.  As mentioned in the man page, it does *not*
-guarantee a NULL-terminated buffer, which makes it extremely dangerous to use.
-It also zeros trailing destination bytes out to the specified length.  Instead,
-use this similar function when possible, but note its different signature:
-void pstrcpy(char *dest, int dest_buf_size, const char *src)
-
-Don't use strcat because it can't check for buffer overflows, but:
-char *pstrcat(char *buf, int buf_size, const char *s)
-
-The same limitation exists with sprintf and vsprintf, so use snprintf and
-vsnprintf.
-
-QEMU provides other useful string functions:
-int strstart(const char *str, const char *val, const char **ptr)
-int stristart(const char *str, const char *val, const char **ptr)
-int qemu_strnlen(const char *s, int max_len)
-
-There are also replacement character processing macros for isxyz and toxyz,
-so instead of e.g. isalnum you should use qemu_isalnum.
-
-Because of the memory management rules, you must use g_strdup/g_strndup
-instead of plain strdup/strndup.
-
-5. Printf-style functions
-
-Whenever you add a new printf-style function, i.e., one with a format
-string argument and following "..." in its prototype, be sure to use
-gcc's printf attribute directive in the prototype.
-
-This makes it so gcc's -Wformat and -Wformat-security options can do
-their jobs and cross-check format strings with the number and types
-of arguments.
-
-6. C standard, implementation defined and undefined behaviors
-
-C code in QEMU should be written to the C99 language specification. A copy
-of the final version of the C99 standard with corrigenda TC1, TC2, and TC3
-included, formatted as a draft, can be downloaded from:
- http://www.open-std.org/jtc1/sc22/WG14/www/docs/n1256.pdf
-
-The C language specification defines regions of undefined behavior and
-implementation defined behavior (to give compiler authors enough leeway to
-produce better code).  In general, code in QEMU should follow the language
-specification and avoid both undefined and implementation defined
-constructs. ("It works fine on the gcc I tested it with" is not a valid
-argument...) However there are a few areas where we allow ourselves to
-assume certain behaviors because in practice all the platforms we care about
-behave in the same way and writing strictly conformant code would be
-painful. These are:
- * you may assume that integers are 2s complement representation
- * you may assume that right shift of a signed integer duplicates
-   the sign bit (ie it is an arithmetic shift, not a logical shift)
-
-In addition, QEMU assumes that the compiler does not use the latitude
-given in C99 and C11 to treat aspects of signed '<<' as undefined, as
-documented in the GNU Compiler Collection manual starting at version 4.0.
-
-7. Error handling and reporting
-
-7.1 Reporting errors to the human user
-
-Do not use printf(), fprintf() or monitor_printf().  Instead, use
-error_report() or error_vreport() from error-report.h.  This ensures the
-error is reported in the right place (current monitor or stderr), and in
-a uniform format.
-
-Use error_printf() & friends to print additional information.
-
-error_report() prints the current location.  In certain common cases
-like command line parsing, the current location is tracked
-automatically.  To manipulate it manually, use the loc_*() from
-error-report.h.
-
-7.2 Propagating errors
-
-An error can't always be reported to the user right where it's detected,
-but often needs to be propagated up the call chain to a place that can
-handle it.  This can be done in various ways.
-
-The most flexible one is Error objects.  See error.h for usage
-information.
-
-Use the simplest suitable method to communicate success / failure to
-callers.  Stick to common methods: non-negative on success / -1 on
-error, non-negative / -errno, non-null / null, or Error objects.
-
-Example: when a function returns a non-null pointer on success, and it
-can fail only in one way (as far as the caller is concerned), returning
-null on failure is just fine, and certainly simpler and a lot easier on
-the eyes than propagating an Error object through an Error ** parameter.
-
-Example: when a function's callers need to report details on failure
-only the function really knows, use Error **, and set suitable errors.
-
-Do not report an error to the user when you're also returning an error
-for somebody else to handle.  Leave the reporting to the place that
-consumes the error returned.
-
-7.3 Handling errors
-
-Calling exit() is fine when handling configuration errors during
-startup.  It's problematic during normal operation.  In particular,
-monitor commands should never exit().
-
-Do not call exit() or abort() to handle an error that can be triggered
-by the guest (e.g., some unimplemented corner case in guest code
-translation or device emulation).  Guests should not be able to
-terminate QEMU.
-
-Note that &error_fatal is just another way to exit(1), and &error_abort
-is just another way to abort().
diff --git a/README b/README.rst
index 441c33eb2f..7497709291 100644
--- a/README
+++ b/README.rst
@@ -1,5 +1,6 @@
-         QEMU README
-         ===========
+===========
+QEMU README
+===========
 
 QEMU is a generic and open source machine & userspace emulator and
 virtualizer.
@@ -37,6 +38,9 @@ QEMU is multi-platform software intended to be buildable on all modern
 Linux platforms, OS-X, Win32 (via the Mingw64 toolchain) and a variety
 of other UNIX targets. The simple steps to build QEMU are:
 
+
+.. code-block:: shell
+
   mkdir build
   cd build
   ../configure
@@ -44,9 +48,9 @@ of other UNIX targets. The simple steps to build QEMU are:
 
 Additional information can also be found online via the QEMU website:
 
-  https://qemu.org/Hosts/Linux
-  https://qemu.org/Hosts/Mac
-  https://qemu.org/Hosts/W32
+* `<https://qemu.org/Hosts/Linux>`_
+* `<https://qemu.org/Hosts/Mac>`_
+* `<https://qemu.org/Hosts/W32>`_
 
 
 Submitting patches
@@ -54,24 +58,29 @@ Submitting patches
 
 The QEMU source code is maintained under the GIT version control system.
 
+.. code-block:: shell
+
    git clone https://git.qemu.org/git/qemu.git
 
 When submitting patches, one common approach is to use 'git
 format-patch' and/or 'git send-email' to format & send the mail to the
 qemu-devel@nongnu.org mailing list. All patches submitted must contain
 a 'Signed-off-by' line from the author. Patches should follow the
-guidelines set out in the HACKING and CODING_STYLE files.
+guidelines set out in the CODING_STYLE.rst file.
 
 Additional information on submitting patches can be found online via
 the QEMU website
 
-  https://qemu.org/Contribute/SubmitAPatch
-  https://qemu.org/Contribute/TrivialPatches
+* `<https://qemu.org/Contribute/SubmitAPatch>`_
+* `<https://qemu.org/Contribute/TrivialPatches>`_
 
 The QEMU website is also maintained under source control.
 
+.. code-block:: shell
+
   git clone https://git.qemu.org/git/qemu-web.git
-  https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/
+
+* `<https://www.qemu.org/2017/02/04/the-new-qemu-website-is-up/>`_
 
 A 'git-publish' utility was created to make above process less
 cumbersome, and is highly recommended for making regular contributions,
@@ -82,10 +91,12 @@ manually for once.
 
 For installation instructions, please go to
 
-  https://github.com/stefanha/git-publish
+*  `<https://github.com/stefanha/git-publish>`_
 
 The workflow with 'git-publish' is:
 
+.. code-block:: shell
+
   $ git checkout master -b my-feature
   $ # work on new commits, add your 'Signed-off-by' lines to each
   $ git publish
@@ -95,6 +106,8 @@ back to it in the future.
 
 Sending v2:
 
+.. code-block:: shell
+
   $ git checkout my-feature # same topic branch
   $ # making changes to the commits (using 'git rebase', for example)
   $ git publish
@@ -109,7 +122,7 @@ The QEMU project uses Launchpad as its primary upstream bug tracker. Bugs
 found when running code built from QEMU git or upstream released sources
 should be reported via:
 
-  https://bugs.launchpad.net/qemu/
+* `<https://bugs.launchpad.net/qemu/>`_
 
 If using QEMU via an operating system vendor pre-built binary package, it
 is preferable to report bugs to the vendor's own bug tracker first. If
@@ -118,7 +131,7 @@ reported via launchpad.
 
 For additional information on bug reporting consult:
 
-  https://qemu.org/Contribute/ReportABug
+* `<https://qemu.org/Contribute/ReportABug>`_
 
 
 Contact
@@ -127,13 +140,11 @@ Contact
 The QEMU community can be contacted in a number of ways, with the two
 main methods being email and IRC
 
- - qemu-devel@nongnu.org
-   https://lists.nongnu.org/mailman/listinfo/qemu-devel
- - #qemu on irc.oftc.net
+* `<mailto:qemu-devel@nongnu.org>`_
+* `<https://lists.nongnu.org/mailman/listinfo/qemu-devel>`_
+* #qemu on irc.oftc.net
 
 Information on additional methods of contacting the community can be
 found online via the QEMU website:
 
-  https://qemu.org/Contribute/StartHere
-
--- End
+* `<https://qemu.org/Contribute/StartHere>`_
diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
index d24c9441ee..aa9a354a0e 100755
--- a/scripts/checkpatch.pl
+++ b/scripts/checkpatch.pl
@@ -461,7 +461,7 @@ sub top_of_kernel_tree {
 
 	my @tree_check = (
 		"COPYING", "MAINTAINERS", "Makefile",
-		"README", "docs", "VERSION",
+		"README.rst", "docs", "VERSION",
 		"vl.c"
 	);