X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ianmdlvl/git?a=blobdiff_plain;f=m4%2Fattributes.m4;h=51ac88be61875444b52737cf85141d8de2255adf;hb=HEAD;hp=ac3c6624cde45ff8ecacd6a093390bc70570a6ee;hpb=3f85ef0f05ffc51e19f86fb83a1c51e8e3cd6817;p=elogind.git

diff --git a/m4/attributes.m4 b/m4/attributes.m4
index ac3c6624c..51ac88be6 100644
--- a/m4/attributes.m4
+++ b/m4/attributes.m4
@@ -34,15 +34,19 @@ dnl this special exception to the GPL to apply to your modified version as
 dnl well.
 
 dnl Check if FLAG in ENV-VAR is supported by compiler and append it
-dnl to WHERE-TO-APPEND variable
-dnl CC_CHECK_FLAG_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG])
+dnl to WHERE-TO-APPEND variable. Note that we invert -Wno-* checks to
+dnl -W* as gcc cannot test for negated warnings. If a C snippet is passed,
+dnl use it, otherwise use a simple main() definition that just returns 0.
+dnl CC_CHECK_FLAG_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG], [C-SNIPPET])
 
 AC_DEFUN([CC_CHECK_FLAG_APPEND], [
   AC_CACHE_CHECK([if $CC supports flag $3 in envvar $2],
                  AS_TR_SH([cc_cv_$2_$3]),
           [eval "AS_TR_SH([cc_save_$2])='${$2}'"
-           eval "AS_TR_SH([$2])='-Werror $3'"
-           AC_LINK_IFELSE([AC_LANG_SOURCE([int main(void) { return 0; } ])],
+           eval "AS_TR_SH([$2])='${cc_save_$2} -Werror `echo "$3" | sed 's/^-Wno-/-W/'`'"
+           AC_LINK_IFELSE([AC_LANG_SOURCE(ifelse([$4], [],
+                                                 [int main(void) { return 0; } ],
+                                                 [$4]))],
                           [eval "AS_TR_SH([cc_cv_$2_$3])='yes'"],
                           [eval "AS_TR_SH([cc_cv_$2_$3])='no'"])
            eval "AS_TR_SH([$2])='$cc_save_$2'"])
@@ -51,10 +55,10 @@ AC_DEFUN([CC_CHECK_FLAG_APPEND], [
         [eval "$1='${$1} $3'"])
 ])
 
-dnl CC_CHECK_FLAGS_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG1 FLAG2])
+dnl CC_CHECK_FLAGS_APPEND([WHERE-TO-APPEND], [ENV-VAR], [FLAG1 FLAG2], [C-SNIPPET])
 AC_DEFUN([CC_CHECK_FLAGS_APPEND], [
-  for flag in $3; do
-    CC_CHECK_FLAG_APPEND($1, $2, $flag)
+  for flag in [$3]; do
+    CC_CHECK_FLAG_APPEND([$1], [$2], $flag, [$4])
   done
 ])