1 files changed, 51 insertions, 1 deletions
diff --git a/meson.build b/meson.build
index 515e31973a..2d3e468730 100644
--- a/meson.build
+++ b/meson.build
@@ -190,10 +190,50 @@ endif
 # Compiler flags #
 ##################
 
-qemu_common_flags = config_host['QEMU_CFLAGS'].split()
+# default flags for all hosts
+# We use -fwrapv to tell the compiler that we require a C dialect where
+# left shift of signed integers is well defined and has the expected
+# 2s-complement style results. (Both clang and gcc agree that it
+# provides these semantics.)
+
+qemu_common_flags = [
+  '-D_GNU_SOURCE', '-D_FILE_OFFSET_BITS=64', '-D_LARGEFILE_SOURCE',
+  '-fno-strict-aliasing', '-fno-common', '-fwrapv' ]
 qemu_cflags = []
 qemu_ldflags = []
 
+if targetos == 'darwin'
+  # Disable attempts to use ObjectiveC features in os/object.h since they
+  # won't work when we're compiling with gcc as a C compiler.
+  qemu_common_flags += '-DOS_OBJECT_USE_OBJC=0'
+elif targetos == 'solaris'
+  # needed for CMSG_ macros in sys/socket.h
+  qemu_common_flags += '-D_XOPEN_SOURCE=600'
+  # needed for TIOCWIN* defines in termios.h
+  qemu_common_flags += '-D__EXTENSIONS__'
+elif targetos == 'haiku'
+  qemu_common_flags += ['-DB_USE_POSITIVE_POSIX_ERRORS', '-D_BSD_SOURCE', '-fPIC']
+endif
+
+# __sync_fetch_and_and requires at least -march=i486. Many toolchains
+# use i686 as default anyway, but for those that don't, an explicit
+# specification is necessary
+if host_arch == 'i386' and not cc.links('''
+  static int sfaa(int *ptr)
+  {
+    return __sync_fetch_and_and(ptr, 0);
+  }
+
+  int main(void)
+  {
+    int val = 42;
+    val = __sync_val_compare_and_swap(&val, 0, 1);
+    sfaa(&val);
+    return val;
+  }''')
+  qemu_common_flags = ['-march=i486'] + qemu_common_flags
+endif
+
 if get_option('gprof')
   qemu_common_flags += ['-p']
   qemu_ldflags += ['-p']
@@ -203,6 +243,16 @@ if get_option('prefer_static')
   qemu_ldflags += get_option('b_pie') ? '-static-pie' : '-static'
 endif
 
+# Meson currently only handles pie as a boolean for now, so if the user
+# has explicitly disabled PIE we need to extend our cflags.
+if not get_option('b_pie')
+  qemu_common_flags += cc.get_supported_arguments('-fno-pie')
+  if not get_option('prefer_static')
+    # No PIE is implied by -static which we added above.
+    qemu_ldflags += cc.get_supported_link_arguments('-no-pie')
+  endif
+endif
+
 if not get_option('stack_protector').disabled()
   stack_protector_probe = '''
     int main(int argc, char *argv[])