Fix sparc64 build with -DNO_ASM and reduce compiler warnings.

[cln.git] / m4 / cc.m4

diff --git a/m4/cc.m4 b/m4/cc.m4
index 0f071e57d08ca457feb780209c522fa1d7af309c..768dba1d600eae55fb66b7cbbbc54dbd31910099 100644 (file)
--- a/m4/cc.m4
+++ b/m4/cc.m4
@@ -18,14 +18,77 @@ fi
 
 
 dnl Wrapper around AC_PROG_CXX setting CXXFLAGS to plain "-O" as opposed to
-dnl "-g -O2" for the GNU compiler (unless CXXFLAGS was set before).
+dnl "-g -O2" for the GNU compiler (unless CXXFLAGS was set before).  Also
+dnl emits a warning if G++ is used and optimization turned off.
 AC_DEFUN([CL_PROG_CXX],
 [cl_test_CXXFLAGS=${CXXFLAGS+set}
 # Make sure this macro does not come after AC_PROG_CXX.
 # Otherwise CXXFLAGS would already be set.
 AC_BEFORE([$0],[AC_PROG_CXX])dnl
 AC_PROG_CXX([$1])
-if test "$cl_test_CXXFLAGS" != set && test "$ac_compiler_gnu" = yes; then
+if test "$ac_compiler_gnu" = yes; then
+  if test "$cl_test_CXXFLAGS" != set; then
+    # User has not set CXXFLAGS.
     CXXFLAGS="-O"
+  else
+    # Warn if optimization has been turned off with GCC.
+    # Optimization is used for module ordering.
+    case $CXXFLAGS in
+      [ *\ -O | -O | -O\ * | *\ -O\ * | -O[!0]* | *\ -O[!0]*) ;; ]
+      *) AC_MSG_WARN([Optimization turned off. I recommend you unset CXXFLAGS.]);;
+    esac
+  fi
+fi
+])
+
+
+dnl Checks whether the stack can be marked nonexecutable by passing an option
+dnl to the C-compiler when acting on .s files. Appends that option to ASFLAGS.
+dnl This macro is adapted from one found in GLIBC-2.3.5.
+AC_DEFUN([CL_AS_NOEXECSTACK],[
+AC_REQUIRE([AC_PROG_CC])
+AC_CACHE_CHECK([whether --noexecstack is desirable for .s files], cl_cv_as_noexecstack, [dnl
+  cat > conftest.c <<EOF
+void foo() {}
+EOF
+  if AC_TRY_COMMAND([${CC} $CFLAGS $CPPFLAGS
+                     -S -o conftest.s conftest.c >/dev/null]) \
+     && grep -q .note.GNU-stack conftest.s \
+     && AC_TRY_COMMAND([${CC} $CFLAGS $CPPFLAGS -Wa,--noexecstack
+                       -c -o conftest.o conftest.s >/dev/null])
+  then
+    cl_cv_as_noexecstack=yes
+  else
+    cl_cv_as_noexecstack=no
+  fi
+  rm -f conftest*])
+  if test "$cl_cv_as_noexecstack" = yes; then
+    ASMFLAGS="$ASMFLAGS -Wa,--noexecstack"
+  fi
+  AC_SUBST(ASMFLAGS)
+])
+
+
+dnl Checks whether the compiler supports __attribute__((flatten)).
+AC_DEFUN([CL_ATTRIBUTE_FLATTEN],[
+AC_REQUIRE([AC_PROG_CXX])
+AC_CACHE_CHECK([whether the compiler supports __attribute__((flatten))], cl_cv_have_attr_flatten, [dnl
+  cat > conftest.cc <<EOF
+void f() __attribute__((flatten));
+EOF
+if AC_TRY_COMMAND(${CXX-g++} $CXXFLAGS -c conftest.cc >/dev/null 2>conftest.stderr)
+then
+  if grep -i "warning" conftest.stderr > /dev/null; then
+    cl_cv_have_attr_flatten=no
+  else
+    cl_cv_have_attr_flatten=yes
+  fi
+else
+  cl_cv_have_attr_flatten=no
+fi
+rm -f conftest*
+])
+if test $cl_cv_have_attr_flatten = yes; then
+  AC_DEFINE(CL_HAVE_ATTRIBUTE_FLATTEN)
 fi
 ])