Import GNULIB's GCC warning macros

GNULIB has a helpful module 'manywarnings' which makes it easy
to turn on every single GCC warning. The general goal is that
every possible GCC warning should be enabled, except for certain
blacklisted warnings.

This imports the GNULIB m4 macros, and updates configure.ac to
use this new capability. As & when new GCC warnings are created,
the 'manywarnings.m4' can be refreshed from upstream GNULIB

* m4/manywarnings.m4, m4/warnings.m4: GNULIB warning macros
* configure.ac: Remove custom compiler warning checks
* m4/spice-compile-warnings.m4: Decide what GCC warnings to enable

1 files changed, 184 insertions, 0 deletions

diff --git a/m4/manywarnings.m4 b/m4/manywarnings.m4
new file mode 100644
index 0000000..fd0e372
--- /dev/null
+++ b/m4/manywarnings.m4
@@ -0,0 +1,184 @@
+# manywarnings.m4 serial 3
+dnl Copyright (C) 2008-2012 Free Software Foundation, Inc.
+dnl This file is free software; the Free Software Foundation
+dnl gives unlimited permission to copy and/or distribute it,
+dnl with or without modifications, as long as this notice is preserved.
+
+dnl From Simon Josefsson
+
+# gl_MANYWARN_COMPLEMENT(OUTVAR, LISTVAR, REMOVEVAR)
+# --------------------------------------------------
+# Copy LISTVAR to OUTVAR except for the entries in REMOVEVAR.
+# Elements separated by whitespace.  In set logic terms, the function
+# does OUTVAR = LISTVAR \ REMOVEVAR.
+AC_DEFUN([gl_MANYWARN_COMPLEMENT],
+[
+  gl_warn_set=
+  set x $2; shift
+  for gl_warn_item
+  do
+    case " $3 " in
+      *" $gl_warn_item "*)
+        ;;
+      *)
+        gl_warn_set="$gl_warn_set $gl_warn_item"
+        ;;
+    esac
+  done
+  $1=$gl_warn_set
+])
+
+# gl_MANYWARN_ALL_GCC(VARIABLE)
+# -----------------------------
+# Add all documented GCC warning parameters to variable VARIABLE.
+# Note that you need to test them using gl_WARN_ADD if you want to
+# make sure your gcc understands it.
+AC_DEFUN([gl_MANYWARN_ALL_GCC],
+[
+  dnl First, check if -Wno-missing-field-initializers is needed.
+  dnl -Wmissing-field-initializers is implied by -W, but that issues
+  dnl warnings with GCC version before 4.7, for the common idiom
+  dnl of initializing types on the stack to zero, using { 0, }
+  AC_REQUIRE([AC_PROG_CC])
+  if test -n "$GCC"; then
+
+    dnl First, check -W -Werror -Wno-missing-field-initializers is supported
+    dnl with the current $CC $CFLAGS $CPPFLAGS.
+    AC_MSG_CHECKING([whether -Wno-missing-field-initializers is supported])
+    AC_CACHE_VAL([gl_cv_cc_nomfi_supported], [
+      gl_save_CFLAGS="$CFLAGS"
+      CFLAGS="$CFLAGS -W -Werror -Wno-missing-field-initializers"
+      AC_COMPILE_IFELSE(
+        [AC_LANG_PROGRAM([[]], [[]])],
+        [gl_cv_cc_nomfi_supported=yes],
+        [gl_cv_cc_nomfi_supported=no])
+      CFLAGS="$gl_save_CFLAGS"])
+    AC_MSG_RESULT([$gl_cv_cc_nomfi_supported])
+
+    if test "$gl_cv_cc_nomfi_supported" = yes; then
+      dnl Now check whether -Wno-missing-field-initializers is needed
+      dnl for the { 0, } construct.
+      AC_MSG_CHECKING([whether -Wno-missing-field-initializers is needed])
+      AC_CACHE_VAL([gl_cv_cc_nomfi_needed], [
+        gl_save_CFLAGS="$CFLAGS"
+        CFLAGS="$CFLAGS -W -Werror"
+        AC_COMPILE_IFELSE(
+          [AC_LANG_PROGRAM(
+             [[void f (void)
+               {
+                 typedef struct { int a; int b; } s_t;
+                 s_t s1 = { 0, };
+               }
+             ]],
+             [[]])],
+          [gl_cv_cc_nomfi_needed=no],
+          [gl_cv_cc_nomfi_needed=yes])
+        CFLAGS="$gl_save_CFLAGS"
+      ])
+      AC_MSG_RESULT([$gl_cv_cc_nomfi_needed])
+    fi
+  fi
+
+  gl_manywarn_set=
+  for gl_manywarn_item in \
+    -Wall \
+    -W \
+    -Wformat-y2k \
+    -Wformat-nonliteral \
+    -Wformat-security \
+    -Winit-self \
+    -Wmissing-include-dirs \
+    -Wswitch-default \
+    -Wswitch-enum \
+    -Wunused \
+    -Wunknown-pragmas \
+    -Wstrict-aliasing \
+    -Wstrict-overflow \
+    -Wsystem-headers \
+    -Wfloat-equal \
+    -Wtraditional \
+    -Wtraditional-conversion \
+    -Wdeclaration-after-statement \
+    -Wundef \
+    -Wshadow \
+    -Wunsafe-loop-optimizations \
+    -Wpointer-arith \
+    -Wbad-function-cast \
+    -Wc++-compat \
+    -Wcast-qual \
+    -Wcast-align \
+    -Wwrite-strings \
+    -Wconversion \
+    -Wsign-conversion \
+    -Wlogical-op \
+    -Waggregate-return \
+    -Wstrict-prototypes \
+    -Wold-style-definition \
+    -Wmissing-prototypes \
+    -Wmissing-declarations \
+    -Wmissing-noreturn \
+    -Wmissing-format-attribute \
+    -Wpacked \
+    -Wpadded \
+    -Wredundant-decls \
+    -Wnested-externs \
+    -Wunreachable-code \
+    -Winline \
+    -Winvalid-pch \
+    -Wlong-long \
+    -Wvla \
+    -Wvolatile-register-var \
+    -Wdisabled-optimization \
+    -Wstack-protector \
+    -Woverlength-strings \
+    -Wbuiltin-macro-redefined \
+    -Wmudflap \
+    -Wpacked-bitfield-compat \
+    -Wsync-nand \
+    ; do
+    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
+  done
+  # The following are not documented in the manual but are included in
+  # output from gcc --help=warnings.
+  for gl_manywarn_item in \
+    -Wattributes \
+    -Wcoverage-mismatch \
+    -Wmultichar \
+    -Wunused-macros \
+    ; do
+    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
+  done
+  # More warnings from gcc 4.6.2 --help=warnings.
+  for gl_manywarn_item in \
+    -Wabi \
+    -Wcpp \
+    -Wdeprecated \
+    -Wdeprecated-declarations \
+    -Wdiv-by-zero \
+    -Wdouble-promotion \
+    -Wendif-labels \
+    -Wextra \
+    -Wformat-contains-nul \
+    -Wformat-extra-args \
+    -Wformat-zero-length \
+    -Wformat=2 \
+    -Wmultichar \
+    -Wnormalized=nfc \
+    -Woverflow \
+    -Wpointer-to-int-cast \
+    -Wpragmas \
+    -Wsuggest-attribute=const \
+    -Wsuggest-attribute=noreturn \
+    -Wsuggest-attribute=pure \
+    -Wtrampolines \
+    ; do
+    gl_manywarn_set="$gl_manywarn_set $gl_manywarn_item"
+  done
+
+  # Disable the missing-field-initializers warning if needed
+  if test "$gl_cv_cc_nomfi_needed" = yes; then
+    gl_manywarn_set="$gl_manywarn_set -Wno-missing-field-initializers"
+  fi
+
+  $1=$gl_manywarn_set
+])