Strict prototype are better for portability and to avoid bugs because it
makes sure the compiler has the information to properly validate the
arguments given when a function is called.
This flag however need special care when checking for it, because the
declaration for 'main' generated by autoconf cannot be a strict prototype
so the detection would always see the flag as failing.
This patch handles this by creating a dedicated macro for this detection
which uses a good prototype because we're in a case where it is possible,
so the detection will not always fail; it also makes sure to add the flag
to CFLAG only at the end, to avoid falsely crashing any further test done
in the configure script.
Signed-off-by: Christophe CURIS <christophe.cu...@free.fr>
---
configure.ac | 5 +++++
m4/wm_cflags_check.m4 | 40 +++++++++++++++++++++++++++++++++++++++-
2 files changed, 44 insertions(+), 1 deletion(-)
diff --git a/configure.ac b/configure.ac
index cc3e046..d46923e 100644
--- a/configure.ac
+++ b/configure.ac
@@ -129,6 +129,11 @@ AS_IF([test "x$debug" = "xyes"],
dnl more difficult, so try to avoid it
AX_CFLAGS_GCC_OPTION([-Wredundant-decls])
dnl
+ dnl Prototype of function must be explicit, no deprecated K&R syntax
+ dnl and no empty argument list which prevents compiler from doing
+ dnl type checking when using the function
+ WM_CFLAGS_GCC_OPTION_STRICTPROTO
+ dnl
dnl Proper attributes helps the compiler to produce better code
WM_CFLAGS_CHECK_FIRST([format attribute suggest],
[-Wsuggest-attribute=format dnl new gcc syntax
diff --git a/m4/wm_cflags_check.m4 b/m4/wm_cflags_check.m4
index 26745b6..b61b16d 100644
--- a/m4/wm_cflags_check.m4
+++ b/m4/wm_cflags_check.m4
@@ -122,6 +122,44 @@ _ACEOF
])
+# WM_CFLAGS_GCC_OPTION_STRICTPROTO
+# --------------------------------
+#
+# Check if the compiler support '-Wstrict-prototypes'. This would be done
+# traditionally using AX_CFLAGS_GCC_OPTION(...), but in the present case it
+# always fail because the test program generated by autoconf always use a
+# non-compliant prototype (this is needed for portability to avoid possible
+# function declaration mismatch on 'main').
+#
+# This macro works around this by providing a strict prototype for 'main'
+# in this case because we are in a very known case.
+AC_DEFUN([WM_CFLAGS_GCC_OPTION_STRICTPROTO],
+[AC_CACHE_CHECK([CFLAGS for gcc -Wstrict-prototypes],
[wm_cv_c_checks_compopt_Wstrict_prototypes],
+ [AC_LANG_COMPILER_REQUIRE()dnl
+ AC_LANG_PUSH([C])
+ wm_save_CFLAGS="$CFLAGS"
+ CFLAGS="$wm_save_CFLAGS -pedantic -Werror -Wstrict-prototypes"
+ AC_COMPILE_IFELSE(
+ [AC_LANG_SOURCE([dnl
+int
+main(int argc, char **argv)
+{
+ /* to avoid failing on -Wunused-parameter */
+ (void) argc;
+ (void) argv;
+
+ return 0;
+}])],
+ [wm_cv_c_checks_compopt_Wstrict_prototypes="-Wstrict-prototypes"],
+ [wm_cv_c_checks_compopt_Wstrict_prototypes="no"])
+ CFLAGS="$wm_save_CFLAGS"
+ AC_LANG_POP([C]) ])
+# We cannot add this flag now to CFLAGS because it could break all further
+# detections done by configure, the flag will be added at the end by the
+# macro WM_CFLAGS_GCC_OPTION_POSTPONED
+])
+
+
# WM_CFLAGS_GCC_OPTION_POSTPONED
# ------------------------------
#
@@ -133,7 +171,7 @@ _ACEOF
AC_DEFUN_ONCE([WM_CFLAGS_GCC_OPTION_POSTPONED],
[# WM_CFLAGS_GCC_OPTION_POSTPONED: add compiler flags at the end of the
autoconf flow
AS_IF([test "x$debug" = "xyes"],
- [m4_foreach([arg_name], [[Wunused_macros]],
+ [m4_foreach([arg_name], [[Wstrict_prototypes], [Wunused_macros]],
[AS_CASE([$wm_cv_c_checks_compopt_[]arg_name],
[no*], [],
[AS_IF([echo " $CFLAGS " | grep " $wm_cv_c_checks_compopt_[]arg_name "
2>&1 > /dev/null],
--
2.1.3
--
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