Merge #17703: build: Improve configure.ac formatting

3ab18246254019896132d1cdb8af2dcdb213ec3b build: Use dnl for all comments in configure.ac, rather than # (fanquake)
8ddcbb4e41fa91e7f80efe6d9c4d5e9bb1355036 build: Remove backticks from configure.ac (fanquake)

Pull request description:

  Use `dnl` for all comments, rather than `#`.
  Remove backticks - Their usage for the `bdb_prefix` and `qt5_prefix` commands may have improved backwards compatibility in some cases, however we now require recent versions of macOS. I'm not sure why they were being used in the `HAVE_STD__SYSTEM` and `HAVE_WSYSTEM` defines.

ACKs for top commit:
  dongcarl:
    ACK 3ab18246254019896132d1cdb8af2dcdb213ec3b
  hebasto:
    ACK 3ab18246254019896132d1cdb8af2dcdb213ec3b, I have reviewed the code and it looks OK, I agree it can be merged.

Tree-SHA512: 2bcffb52c365acff87a0e6b9527ae31f36fdabb7ea095a8fd261f9a39b2c2848f5dfc148bc38d21e21e7bd761b1a2960e9a96f508c66be84d9569b8a401e812a

1 files changed, 54 insertions, 55 deletions

diff --git a/configure.ac b/configure.ac
index e0bec0882e..e7d14202a7 100644
--- a/configure.ac
+++ b/configure.ac
@@ -243,27 +243,27 @@ AC_ARG_ENABLE(man,
     enable_man=yes)
 AM_CONDITIONAL(ENABLE_MAN, test "$enable_man" != no)
 
-# Enable debug
+dnl Enable debug
 AC_ARG_ENABLE([debug],
     [AS_HELP_STRING([--enable-debug],
                     [use compiler flags and macros suited for debugging (default is no)])],
     [enable_debug=$enableval],
     [enable_debug=no])
 
-# Enable different -fsanitize options
+dnl Enable different -fsanitize options
 AC_ARG_WITH([sanitizers],
     [AS_HELP_STRING([--with-sanitizers],
                     [comma separated list of extra sanitizers to build with (default is none enabled)])],
     [use_sanitizers=$withval])
 
-# Enable gprof profiling
+dnl Enable gprof profiling
 AC_ARG_ENABLE([gprof],
     [AS_HELP_STRING([--enable-gprof],
                     [use gprof profiling compiler flags (default is no)])],
     [enable_gprof=$enableval],
     [enable_gprof=no])
 
-# Turn warnings into errors
+dnl Turn warnings into errors
 AC_ARG_ENABLE([werror],
     [AS_HELP_STRING([--enable-werror],
                     [Treat certain compiler warnings as errors (default is no)])],
@@ -274,15 +274,15 @@ AC_LANG_PUSH([C++])
 AX_CHECK_COMPILE_FLAG([-Werror],[CXXFLAG_WERROR="-Werror"],[CXXFLAG_WERROR=""])
 
 if test "x$enable_debug" = xyes; then
-  # Clear default -g -O2 flags
+  dnl Clear default -g -O2 flags
   if test "x$CXXFLAGS_overridden" = xno; then
 	CXXFLAGS=""
   fi
 
-  # Disable all optimizations
+  dnl Disable all optimizations
   AX_CHECK_COMPILE_FLAG([-O0], [[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -O0"]],,[[$CXXFLAG_WERROR]])
 
-  # Prefer -g3, fall back to -g if that is unavailable.
+  dnl Prefer -g3, fall back to -g if that is unavailable.
   AX_CHECK_COMPILE_FLAG(
     [-g3],
     [[DEBUG_CXXFLAGS="$DEBUG_CXXFLAGS -g3"]],
@@ -295,19 +295,19 @@ if test "x$enable_debug" = xyes; then
 fi
 
 if test x$use_sanitizers != x; then
-  # First check if the compiler accepts flags. If an incompatible pair like
-  # -fsanitize=address,thread is used here, this check will fail. This will also
-  # fail if a bad argument is passed, e.g. -fsanitize=undfeined
+  dnl First check if the compiler accepts flags. If an incompatible pair like
+  dnl -fsanitize=address,thread is used here, this check will fail. This will also
+  dnl fail if a bad argument is passed, e.g. -fsanitize=undfeined
   AX_CHECK_COMPILE_FLAG(
     [[-fsanitize=$use_sanitizers]],
     [[SANITIZER_CXXFLAGS=-fsanitize=$use_sanitizers]],
     [AC_MSG_ERROR([compiler did not accept requested flags])])
 
-  # Some compilers (e.g. GCC) require additional libraries like libasan,
-  # libtsan, libubsan, etc. Make sure linking still works with the sanitize
-  # flag. This is a separate check so we can give a better error message when
-  # the sanitize flags are supported by the compiler but the actual sanitizer
-  # libs are missing.
+  dnl Some compilers (e.g. GCC) require additional libraries like libasan,
+  dnl libtsan, libubsan, etc. Make sure linking still works with the sanitize
+  dnl flag. This is a separate check so we can give a better error message when
+  dnl the sanitize flags are supported by the compiler but the actual sanitizer
+  dnl libs are missing.
   AX_CHECK_LINK_FLAG(
     [[-fsanitize=$use_sanitizers]],
     [[SANITIZER_LDFLAGS=-fsanitize=$use_sanitizers]],
@@ -344,9 +344,9 @@ if test "x$CXXFLAGS_overridden" = "xno"; then
   AX_CHECK_COMPILE_FLAG([-Wredundant-decls],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wredundant-decls"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wunused-variable],[WARN_CXXFLAGS="$WARN_CXXFLAGS -Wunused-variable"],,[[$CXXFLAG_WERROR]])
 
-  ## Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
-  ## unknown options if any other warning is produced. Test the -Wfoo case, and
-  ## set the -Wno-foo case if it works.
+  dnl Some compilers (gcc) ignore unknown -Wno-* options, but warn about all
+  dnl unknown options if any other warning is produced. Test the -Wfoo case, and
+  dnl set the -Wno-foo case if it works.
   AX_CHECK_COMPILE_FLAG([-Wunused-parameter],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-parameter"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wself-assign],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-self-assign"],,[[$CXXFLAG_WERROR]])
   AX_CHECK_COMPILE_FLAG([-Wunused-local-typedef],[NOWARN_CXXFLAGS="$NOWARN_CXXFLAGS -Wno-unused-local-typedef"],,[[$CXXFLAG_WERROR]])
@@ -361,9 +361,9 @@ enable_shani=no
 
 if test "x$use_asm" = "xyes"; then
 
-# Check for optional instruction set support. Enabling these does _not_ imply that all code will
-# be compiled with them, rather that specific objects/libs may use them after checking for runtime
-# compatibility.
+dnl Check for optional instruction set support. Enabling these does _not_ imply that all code will
+dnl be compiled with them, rather that specific objects/libs may use them after checking for runtime
+dnl compatibility.
 AX_CHECK_COMPILE_FLAG([-msse4.2],[[SSE42_CXXFLAGS="-msse4.2"]],,[[$CXXFLAG_WERROR]])
 AX_CHECK_COMPILE_FLAG([-msse4.1],[[SSE41_CXXFLAGS="-msse4.1"]],,[[$CXXFLAG_WERROR]])
 AX_CHECK_COMPILE_FLAG([-mavx -mavx2],[[AVX2_CXXFLAGS="-mavx -mavx2"]],,[[$CXXFLAG_WERROR]])
@@ -506,8 +506,8 @@ case $host in
      AC_CHECK_LIB([iphlpapi],      [main],, AC_MSG_ERROR(libiphlpapi missing))
      AC_CHECK_LIB([crypt32],      [main],, AC_MSG_ERROR(libcrypt32 missing))
 
-     # -static is interpreted by libtool, where it has a different meaning.
-     # In libtool-speak, it's -all-static.
+     dnl -static is interpreted by libtool, where it has a different meaning.
+     dnl In libtool-speak, it's -all-static.
      AX_CHECK_LINK_FLAG([[-static]],[LIBTOOL_APP_LDFLAGS="$LIBTOOL_APP_LDFLAGS -all-static"])
 
      AC_PATH_PROG([MAKENSIS], [makensis], none)
@@ -555,8 +555,8 @@ case $host in
          dnl It's safe to add these paths even if the functionality is disabled by
          dnl the user (--without-wallet or --without-gui for example).
 
-         bdb_prefix=`$BREW --prefix berkeley-db4 2>/dev/null`
-         qt5_prefix=`$BREW --prefix qt5 2>/dev/null`
+         bdb_prefix=$($BREW --prefix berkeley-db4 2>/dev/null)
+         qt5_prefix=$($BREW --prefix qt5 2>/dev/null)
          if test x$bdb_prefix != x; then
            CPPFLAGS="$CPPFLAGS -I$bdb_prefix/include"
            LIBS="$LIBS -L$bdb_prefix/lib"
@@ -673,11 +673,11 @@ AC_C_BIGENDIAN
 dnl Check for pthread compile/link requirements
 AX_PTHREAD
 
-# The following macro will add the necessary defines to bitcoin-config.h, but
-# they also need to be passed down to any subprojects. Pull the results out of
-# the cache and add them to CPPFLAGS.
+dnl The following macro will add the necessary defines to bitcoin-config.h, but
+dnl they also need to be passed down to any subprojects. Pull the results out of
+dnl the cache and add them to CPPFLAGS.
 AC_SYS_LARGEFILE
-# detect POSIX or GNU variant of strerror_r
+dnl detect POSIX or GNU variant of strerror_r
 AC_FUNC_STRERROR_R
 
 if test x$ac_cv_sys_file_offset_bits != x &&
@@ -700,12 +700,12 @@ AX_GCC_FUNC_ATTRIBUTE([dllimport])
 
 if test x$use_glibc_compat != xno; then
 
-  #glibc absorbed clock_gettime in 2.17. librt (its previous location) is safe to link
-  #in anyway for back-compat.
+  dnl glibc absorbed clock_gettime in 2.17. librt (its previous location) is safe to link
+  dnl in anyway for back-compat.
   AC_CHECK_LIB([rt],[clock_gettime],, AC_MSG_ERROR(librt missing))
 
-  #__fdelt_chk's params and return type have changed from long unsigned int to long int.
-  # See which one is present here.
+  dnl __fdelt_chk's params and return type have changed from long unsigned int to long int.
+  dnl See which one is present here.
   AC_MSG_CHECKING(__fdelt_chk type)
   AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#ifdef _FORTIFY_SOURCE
                     #undef _FORTIFY_SOURCE
@@ -741,22 +741,22 @@ if test "x$enable_gprof" = xyes; then
 fi
 
 if test x$TARGET_OS != xwindows; then
-  # All windows code is PIC, forcing it on just adds useless compile warnings
+  dnl All windows code is PIC, forcing it on just adds useless compile warnings
   AX_CHECK_COMPILE_FLAG([-fPIC],[PIC_FLAGS="-fPIC"])
 fi
 
-# All versions of gcc that we commonly use for building are subject to bug
-# https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set
-# -fstack-reuse=none for all gcc builds. (Only gcc understands this flag)
+dnl All versions of gcc that we commonly use for building are subject to bug
+dnl https://gcc.gnu.org/bugzilla/show_bug.cgi?id=90348. To work around that, set
+dnl -fstack-reuse=none for all gcc builds. (Only gcc understands this flag)
 AX_CHECK_COMPILE_FLAG([-fstack-reuse=none],[HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -fstack-reuse=none"])
 if test x$use_hardening != xno; then
   use_hardening=yes
   AX_CHECK_COMPILE_FLAG([-Wstack-protector],[HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -Wstack-protector"])
   AX_CHECK_COMPILE_FLAG([-fstack-protector-all],[HARDENED_CXXFLAGS="$HARDENED_CXXFLAGS -fstack-protector-all"])
 
-  # When enable_debug is yes, all optimizations are disabled.
-  # However, FORTIFY_SOURCE requires that there is some level of optimization, otherwise it does nothing and just creates a compiler warning.
-  # Since FORTIFY_SOURCE is a no-op without optimizations, do not enable it when enable_debug is yes.
+  dnl When enable_debug is yes, all optimizations are disabled.
+  dnl However, FORTIFY_SOURCE requires that there is some level of optimization, otherwise it does nothing and just creates a compiler warning.
+  dnl Since FORTIFY_SOURCE is a no-op without optimizations, do not enable it when enable_debug is yes.
   if test x$enable_debug != xyes; then
     AX_CHECK_PREPROC_FLAG([-D_FORTIFY_SOURCE=2],[
       AX_CHECK_PREPROC_FLAG([-U_FORTIFY_SOURCE],[
@@ -788,8 +788,8 @@ fi
 
 AC_CHECK_HEADERS([endian.h sys/endian.h byteswap.h stdio.h stdlib.h unistd.h strings.h sys/types.h sys/stat.h sys/select.h sys/prctl.h sys/sysctl.h vm/vm_param.h sys/vmmeter.h sys/resources.h])
 
-# FD_ZERO may be dependent on a declaration of memcpy, e.g. in SmartOS
-# check that it fails to build without memcpy, then that it builds with
+dnl FD_ZERO may be dependent on a declaration of memcpy, e.g. in SmartOS
+dnl check that it fails to build without memcpy, then that it builds with
 AC_MSG_CHECKING(FD_ZERO memcpy dependence)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[
     #include <cstddef>
@@ -827,7 +827,7 @@ AC_CHECK_DECLS([getifaddrs, freeifaddrs],,,
 )
 AC_CHECK_DECLS([strnlen])
 
-# Check for daemon(3), unrelated to --with-daemon (although used by it)
+dnl Check for daemon(3), unrelated to --with-daemon (although used by it)
 AC_CHECK_DECLS([daemon])
 
 AC_CHECK_DECLS([le16toh, le32toh, le64toh, htole16, htole32, htole64, be16toh, be32toh, be64toh, htobe16, htobe32, htobe64],,,
@@ -893,19 +893,19 @@ if test "x$use_thread_local" = xyes || { test "x$use_thread_local" = xauto && te
     [
      case $host in
        *mingw*)
-          # mingw32's implementation of thread_local has also been shown to behave
-          # erroneously under concurrent usage; see:
-          # https://gist.github.com/jamesob/fe9a872051a88b2025b1aa37bfa98605
+          dnl mingw32's implementation of thread_local has also been shown to behave
+          dnl erroneously under concurrent usage; see:
+          dnl https://gist.github.com/jamesob/fe9a872051a88b2025b1aa37bfa98605
           AC_MSG_RESULT(no)
           ;;
         *darwin*)
-          # TODO enable thread_local on later versions of Darwin where it is
-          # supported (per https://stackoverflow.com/a/29929949)
+          dnl TODO enable thread_local on later versions of Darwin where it is
+          dnl supported (per https://stackoverflow.com/a/29929949)
           AC_MSG_RESULT(no)
           ;;
         *freebsd*)
-          # FreeBSD's implementation of thread_local is also buggy (per
-          # https://groups.google.com/d/msg/bsdmailinglist/22ncTZAbDp4/Dii_pII5AwAJ)
+          dnl FreeBSD's implementation of thread_local is also buggy (per
+          dnl https://groups.google.com/d/msg/bsdmailinglist/22ncTZAbDp4/Dii_pII5AwAJ)
           AC_MSG_RESULT(no)
           ;;
         *)
@@ -921,7 +921,7 @@ if test "x$use_thread_local" = xyes || { test "x$use_thread_local" = xauto && te
   LDFLAGS="$TEMP_LDFLAGS"
 fi
 
-# Check for different ways of gathering OS randomness
+dnl Check for different ways of gathering OS randomness
 AC_MSG_CHECKING(for Linux getrandom syscall)
 AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <unistd.h>
   #include <sys/syscall.h>
@@ -975,7 +975,7 @@ AC_COMPILE_IFELSE([AC_LANG_PROGRAM([[#include <stdint.h>
  [ AC_MSG_RESULT(no)]
 )
 
-# Check for reduced exports
+dnl Check for reduced exports
 if test x$use_reduce_exports = xyes; then
   AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],[RE_CXXFLAGS="-fvisibility=hidden"],
   [AC_MSG_ERROR([Cannot set default symbol visibility. Use --disable-reduce-exports.])])
@@ -987,7 +987,7 @@ AC_LINK_IFELSE(
         [[ #include <cstdlib> ]],
         [[ int nErr = std::system(""); ]]
     )],
-    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STD__SYSTEM, 1, Define to 1 if you have the `std::system' function.)],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_STD__SYSTEM, 1, Define to 1 if std::system is available.)],
     [ AC_MSG_RESULT(no) ]
 )
 
@@ -997,11 +997,10 @@ AC_LINK_IFELSE(
         [[ ]],
         [[ int nErr = ::_wsystem(""); ]]
     )],
-    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_WSYSTEM, 1, Define to 1 if you have the `::wsystem' function.)],
+    [ AC_MSG_RESULT(yes); AC_DEFINE(HAVE_WSYSTEM, 1, Define to 1 if ::wsystem is available.)],
     [ AC_MSG_RESULT(no) ]
 )
 
-# Define to 1 if std::system or ::wsystem (Windows) is available
 AC_DEFINE([HAVE_SYSTEM], [HAVE_STD__SYSTEM || HAVE_WSYSTEM], [std::system or ::wsystem])
 
 LEVELDB_CPPFLAGS=