Improve read-write .eh_frame check (#546)

llvm-objdump -h does not print BFD SEC_* constants like "READONLY",
so the check will consider .eh_frame writable.
clang 11 (since https://reviews.llvm.org/D73999) will error for mismatching section flags.

Use readelf -S and check "WA" instead.

diff --git a/configure.ac b/configure.ac
index bf96297270d7ffc8fdca97bfaddf3a85005f4ed6..3ca1f4fbba9264572442dd3dc339b56c759246b9 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -262,17 +262,11 @@ fi
 if test "x$GCC" = "xyes"; then
   AC_CACHE_CHECK([whether .eh_frame section should be read-only],
       libffi_cv_ro_eh_frame, [
-       libffi_cv_ro_eh_frame=no
+       libffi_cv_ro_eh_frame=yes
        echo 'extern void foo (void); void bar (void) { foo (); foo (); }' > conftest.c
        if $CC $CFLAGS -c -fpic -fexceptions -o conftest.o conftest.c > /dev/null 2>&1; then
-           objdump -h conftest.o > conftest.dump 2>&1
-           libffi_eh_frame_line=`grep -n eh_frame conftest.dump | cut -d: -f 1`
-           if test "x$libffi_eh_frame_line" != "x"; then
-               libffi_test_line=`expr $libffi_eh_frame_line + 1`p
-               sed -n $libffi_test_line conftest.dump > conftest.line
-               if grep READONLY conftest.line > /dev/null; then
-                   libffi_cv_ro_eh_frame=yes
-               fi
+           if readelf -WS conftest.o | grep -q -n 'eh_frame .* WA'; then
+               libffi_cv_ro_eh_frame=no
            fi
        fi
        rm -f conftest.*