dnl Use lots of warning flags with with gcc and compatible compilers

dnl Note: if you change the following variable, the cache is automatically

dnl skipped and all flags rechecked.  So there's no need to do anything

dnl else.  If for any reason you need to force a recheck, just change

dnl MAYBE_WARN in an ignorable way (like adding whitespace)

# -Wcast-align generates lots of false positive reports we need to

# cast image data from uint8_t to uin32_t.

# -Wlogical-op causes too much noise from strcmp("literal", str)

MAYBE_WARN="-Wall -Wextra \

-Wmissing-declarations -Werror-implicit-function-declaration \

-Wpointer-arith -Wwrite-strings -Wsign-compare -Wpacked \

-Wswitch-enum -Wmissing-format-attribute -Wvolatile-register-var \

-Wstrict-aliasing=2 -Winit-self -Wunsafe-loop-optimizations \

-Wno-missing-field-initializers -Wno-unused-parameter \

-Wno-attributes -Wno-long-long -Winline"

MAYBE_C_SPECIFIC_WARN="-Wold-style-definition \

-Wdeclaration-after-statement -Wstrict-prototypes \

-Wmissing-prototypes -Wbad-function-cast -Wnested-externs"

# New -Wno options should be added here

# gcc-4.4 and later accept every -Wno- option but may complain later that this

# option is unknow each time another warning happen.

# -Wunused-but-set-variable is too noisy at present

NO_WARN="unused-but-set-variable"

dnl Sun Studio 12 likes to rag at us for abusing enums like

dnl having cairo_status_t variables hold cairo_int_status_t

dnl values.  It's bad, we know.  Now please be quiet.

MAYBE_WARN="$MAYBE_WARN -erroff=E_ENUM_TYPE_MISMATCH_ARG \

			-erroff=E_ENUM_TYPE_MISMATCH_OP"

dnl We also abuse the warning-flag facility to enable other compiler

dnl options.  Namely, the following:

MAYBE_WARN="$MAYBE_WARN -fno-strict-aliasing -fno-common"

dnl Also to turn various gcc/glibc-specific preprocessor checks

MAYBE_WARN="$MAYBE_WARN -Wp,-D_FORTIFY_SOURCE=2"

# invalidate cached value if MAYBE_WARN has changed

if test "x$cairo_cv_warn_maybe" != "x$MAYBE_WARN"; then

	unset cairo_cv_warn_cflags

fi

AC_CACHE_CHECK([for supported warning flags], cairo_cv_warn_cflags, [

	echo

	WARN_CFLAGS=""

	# Some warning options are not supported by all versions of

	# gcc, so test all desired options against the current

	# compiler.

	#

	# Note that there are some order dependencies

	# here. Specifically, an option that disables a warning will

	# have no net effect if a later option then enables that

	# warnings, (perhaps implicitly). So we put some grouped

	# options (-Wall and -Wextra) up front and the -Wno options

	# last.

	for W in $MAYBE_WARN; do

		CAIRO_CC_TRY_FLAG([$W],, [WARN_CFLAGS="$WARN_CFLAGS $W"])

	done

	for W in $NO_WARN; do

		CAIRO_CC_TRY_FLAG([-W$W -Wno-$W],, [WARN_CFLAGS="$WARN_CFLAGS -Wno-$W"])

	done

	cairo_cv_warn_cflags=$WARN_CFLAGS

	cairo_cv_warn_maybe="$MAYBE_WARN $MAYBE_C_SPECIFIC_WARN"

	AC_MSG_CHECKING([which warning flags were supported])

])

WARN_CFLAGS="$cairo_cv_warn_cflags"

CAIRO_CFLAGS="$CAIRO_CFLAGS $WARN_CFLAGS"

# We only wish to enable attribute(warn_unused_result) if we can prevent

# gcc from generating thousands of warnings about the misapplication of the

# attribute to void functions and variables.

AC_CACHE_CHECK([how to enable unused result warnings], cairo_cv_warn_unused_result, [

        AC_REQUIRE([AC_PROG_GREP])

	cairo_cv_warn_unused_result=""

	if echo $WARN_CFLAGS | $GREP -e '-Wno-attributes' >/dev/null; then

	    CAIRO_CC_TRY_FLAG_SILENT(

			[-Wno-attributes],

			[__attribute__((__warn_unused_result__)) void f (void) {}

			 __attribute__((__warn_unused_result__)) int g;],

			[cairo_cv_warn_unused_result="__attribute__((__warn_unused_result__))"])

	fi

])

AC_DEFINE_UNQUOTED([WARN_UNUSED_RESULT], [$cairo_cv_warn_unused_result],

	  [Define to the value your compiler uses to support the warn-unused-result attribute])

dnl check linker flags

AC_CACHE_CHECK([how to allow undefined symbols in shared libraries used by test suite], cairo_cv_test_undefined_ldflags,

	       [CAIRO_CC_TRY_FLAG_SILENT([-Wl,--allow-shlib-undefined], [],

				  [cairo_cv_test_undefined_ldflags="-Wl,--allow-shlib-undefined]")])

CAIRO_TEST_UNDEFINED_LDFLAGS="$cairo_cv_test_undefined_ldflags"

AC_SUBST(CAIRO_TEST_UNDEFINED_LDFLAGS)