Hi people!
The -Wimplicit-fallthrough switch was introduced in GCC 7.
Older version of GCC (like 3 and 4) do not complain when they get passed
an invalid -WFOO option, but GCC 6 bails out like this:
gcc: error: unrecognized command line option '-Wimplicit-fallthrough';
did you mean '-Wno-fallthrough'?
diff --git a/m4/gnulib-common.m4 b/m4/gnulib-common.m4
index 179aac7aa1..62741f830f 100644
--- a/m4/gnulib-common.m4
+++ b/m4/gnulib-common.m4
@@ -896,7 +896,7 @@ AC_DEFUN([gl_CC_GNULIB_WARNINGS],
dnl -Wno-conversion >= 3 >= 3.9
dnl -Wno-float-conversion >= 4.9 >= 3.9
dnl -Wno-float-equal >= 3 >= 3.9
- dnl -Wimplicit-fallthrough >= 3 >= 3.9
+ dnl -Wimplicit-fallthrough >= 7 >= 3.9
dnl -Wno-pedantic >= 4.8 >= 3.9
dnl -Wno-sign-compare >= 3 >= 3.9
dnl -Wno-sign-conversion >= 4.3 >= 3.9
@@ -911,12 +911,14 @@ AC_DEFUN([gl_CC_GNULIB_WARNINGS],
-Wno-cast-qual
-Wno-conversion
-Wno-float-equal
- -Wimplicit-fallthrough
-Wno-sign-compare
-Wno-undef
-Wno-unused-function
-Wno-unused-parameter
#endif
+ #if __GNUC__ => 7 || (__clang_major__ + (__clang_minor__ >= 9) > 3)
+ -Wimplicit-fallthrough
+ #endif
#if __GNUC__ + (__GNUC_MINOR__ >= 9) > 4 || (__clang_major__ +
(__clang_minor__ >= 9) > 3)
-Wno-float-conversion
#endif
