* [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately
@ 2021-02-17 9:27 tbaeder
2021-02-17 9:27 ` [PATCH 2/3] build: Check for -Wtrampolines support tbaeder
` (2 more replies)
0 siblings, 3 replies; 6+ messages in thread
From: tbaeder @ 2021-02-17 9:27 UTC (permalink / raw)
To: elfutils-devel
From: Timm Bäder <tbaeder@redhat.com>
GCC accepts the =5, which means it doesn't try to parse any comments
and only accepts the fallthrough attribute in code. Clang does not ever
parse any comments and always wants the fallthrough attribute anyway.
Clang also doesn't accept the =n parameter for -Wimplicit-fallthrough.
Test for =5 separately and use it if supported and fall back to just
-Wimplicit-fallthrough otherwise.
Signed-off-by: Timm Bäder <tbaeder@redhat.com>
---
config/eu.am | 4 ++++
configure.ac | 12 ++++++++++++
2 files changed, 16 insertions(+)
diff --git a/config/eu.am b/config/eu.am
index 6c3c444f..e109ffd3 100644
--- a/config/eu.am
+++ b/config/eu.am
@@ -64,8 +64,12 @@ endif
if HAVE_IMPLICIT_FALLTHROUGH_WARNING
# Use strict fallthrough. Only __attribute__((fallthrough)) will prevent the
# warning
+if HAVE_IMPLICIT_FALLTHROUGH_5_WARNING
IMPLICIT_FALLTHROUGH_WARNING=-Wimplicit-fallthrough=5
else
+IMPLICIT_FALLTHROUGH_WARNING=-Wimplicit-fallthrough
+endif
+else
IMPLICIT_FALLTHROUGH_WARNING=
endif
diff --git a/configure.ac b/configure.ac
index d345495d..e56aeb6a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -519,6 +519,18 @@ CFLAGS="$old_CFLAGS"])
AM_CONDITIONAL(HAVE_IMPLICIT_FALLTHROUGH_WARNING,
[test "x$ac_cv_implicit_fallthrough" != "xno"])
+# Check whether the compiler additionally accepts -Wimplicit-fallthrough=5
+# GCC accepts this and 5 means "don't parse any fallthrough comments and
+# only accept the fallthrough attribute"
+AC_CACHE_CHECK([whether the compiler accepts -Wimplicit-fallthrough=5], ac_cv_implicit_fallthrough_5, [dnl
+old_CFLAGS="$CFLAGS"
+CFLAGS="$CFLAGS -Wimplicit-fallthrough=5 -Werror"
+AC_COMPILE_IFELSE([AC_LANG_SOURCE([])],
+ ac_cv_implicit_fallthrough_5=yes, ac_cv_implicit_fallthrough_5=no)
+CFLAGS="$old_CFLAGS"])
+AM_CONDITIONAL(HAVE_IMPLICIT_FALLTHROUGH_5_WARNING,
+ [test "x$ac_cv_implicit_fallthrough_5" != "xno"])
+
# Assume the fallthrough attribute is supported if -Wimplict-fallthrough is supported
if test "$ac_cv_implicit_fallthrough" = "yes"; then
AC_DEFINE([HAVE_FALLTHROUGH], [1],
--
2.26.2
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH 2/3] build: Check for -Wtrampolines support 2021-02-17 9:27 [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately tbaeder @ 2021-02-17 9:27 ` tbaeder 2021-03-06 2:07 ` Mark Wielaard 2021-02-17 9:27 ` [PATCH 3/3] build: Check for -Wno-packed-not-aligned support tbaeder 2021-03-06 1:25 ` [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately Mark Wielaard 2 siblings, 1 reply; 6+ messages in thread From: tbaeder @ 2021-02-17 9:27 UTC (permalink / raw) To: elfutils-devel From: Timm Bäder <tbaeder@redhat.com> Clang does not support -Wtrampolines, so check if the compiler supports it before using it. Signed-off-by: Timm Bäder <tbaeder@redhat.com> --- config/eu.am | 10 ++++++++-- configure.ac | 9 +++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/config/eu.am b/config/eu.am index e109ffd3..02512570 100644 --- a/config/eu.am +++ b/config/eu.am @@ -73,8 +73,14 @@ else IMPLICIT_FALLTHROUGH_WARNING= endif +if HAVE_TRAMPOLINES_WARNING +TRAMPOLINES_WARNING=-Wtrampolines +else +TRAMPOLINES_WARNING= +endif + AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \ - -Wold-style-definition -Wstrict-prototypes -Wtrampolines \ + -Wold-style-definition -Wstrict-prototypes $(TRAMPOLINES_WARNING) \ $(LOGICAL_OP_WARNING) $(DUPLICATED_COND_WARNING) \ $(NULL_DEREFERENCE_WARNING) $(IMPLICIT_FALLTHROUGH_WARNING) \ $(if $($(*F)_no_Werror),,-Werror) \ @@ -84,7 +90,7 @@ AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \ $($(*F)_CFLAGS) AM_CXXFLAGS = -std=c++11 -Wall -Wshadow \ - -Wtrampolines \ + $(TRAMPOLINES_WARNING) \ $(LOGICAL_OP_WARNING) $(DUPLICATED_COND_WARNING) \ $(NULL_DEREFERENCE_WARNING) $(IMPLICIT_FALLTHROUGH_WARNING) \ $(if $($(*F)_no_Werror),,-Werror) \ diff --git a/configure.ac b/configure.ac index e56aeb6a..5f3321aa 100644 --- a/configure.ac +++ b/configure.ac @@ -537,6 +537,15 @@ if test "$ac_cv_implicit_fallthrough" = "yes"; then [Defined if __attribute__((fallthrough)) is supported]) fi +AC_CACHE_CHECK([whether the compiler accepts -Wtrampolines], ac_cv_trampolines, [dnl +old_CFLAGS="$CFLAGS" +CFLAGS="$CFLAGS -Wtrampolines -Werror" +AC_COMPILE_IFELSE([AC_LANG_SOURCE([])], + ac_cv_trampolines=yes, ac_cv_trampolines=no) +CFLAGS="$old_CFLAGS"]) +AM_CONDITIONAL(HAVE_TRAMPOLINES_WARNING, + [test "x$ac_cv_trampolines" != "xno"]) + saved_LIBS="$LIBS" AC_SEARCH_LIBS([argp_parse], [argp]) LIBS="$saved_LIBS" -- 2.26.2 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 2/3] build: Check for -Wtrampolines support 2021-02-17 9:27 ` [PATCH 2/3] build: Check for -Wtrampolines support tbaeder @ 2021-03-06 2:07 ` Mark Wielaard 0 siblings, 0 replies; 6+ messages in thread From: Mark Wielaard @ 2021-03-06 2:07 UTC (permalink / raw) To: tbaeder, elfutils-devel Hi Timm, On Wed, 2021-02-17 at 10:27 +0100, Timm Bäder via Elfutils-devel wrote: > From: Timm Bäder <tbaeder@redhat.com> > > Clang does not support -Wtrampolines, so check if the compiler > supports > it before using it. Grin. If you don't support creating trampolines, then having a warning for them (or at least the variant that needs executable stack, which is really what we are trying to prevent) is probably not a high priority. Added ChangeLog entries and pushed. Thanks, Mark ^ permalink raw reply [flat|nested] 6+ messages in thread
* [PATCH 3/3] build: Check for -Wno-packed-not-aligned support 2021-02-17 9:27 [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately tbaeder 2021-02-17 9:27 ` [PATCH 2/3] build: Check for -Wtrampolines support tbaeder @ 2021-02-17 9:27 ` tbaeder 2021-03-06 2:17 ` Mark Wielaard 2021-03-06 1:25 ` [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately Mark Wielaard 2 siblings, 1 reply; 6+ messages in thread From: tbaeder @ 2021-02-17 9:27 UTC (permalink / raw) To: elfutils-devel From: Timm Bäder <tbaeder@redhat.com> Clang does not support this warning, so check for compiler support before using it. Signed-off-by: Timm Bäder <tbaeder@redhat.com> --- config/eu.am | 10 ++++++++-- configure.ac | 9 +++++++++ 2 files changed, 17 insertions(+), 2 deletions(-) diff --git a/config/eu.am b/config/eu.am index 02512570..2c3e4571 100644 --- a/config/eu.am +++ b/config/eu.am @@ -79,6 +79,12 @@ else TRAMPOLINES_WARNING= endif +if HAVE_NO_PACKED_NOT_ALIGNED_WARNING +NO_PACKED_NOT_ALIGNED_WARNING=-Wno-packed-not-aligned +else +NO_PACKED_NOT_ALIGNED_WARNING= +endif + AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \ -Wold-style-definition -Wstrict-prototypes $(TRAMPOLINES_WARNING) \ $(LOGICAL_OP_WARNING) $(DUPLICATED_COND_WARNING) \ @@ -86,7 +92,7 @@ AM_CFLAGS = -std=gnu99 -Wall -Wshadow -Wformat=2 \ $(if $($(*F)_no_Werror),,-Werror) \ $(if $($(*F)_no_Wunused),,-Wunused -Wextra) \ $(if $($(*F)_no_Wstack_usage),,$(STACK_USAGE_WARNING)) \ - $(if $($(*F)_no_Wpacked_not_aligned),-Wno-packed-not-aligned,) \ + $(if $($(*F)_no_Wpacked_not_aligned),$(NO_PACKED_NOT_ALIGNED_WARNING),) \ $($(*F)_CFLAGS) AM_CXXFLAGS = -std=c++11 -Wall -Wshadow \ @@ -96,7 +102,7 @@ AM_CXXFLAGS = -std=c++11 -Wall -Wshadow \ $(if $($(*F)_no_Werror),,-Werror) \ $(if $($(*F)_no_Wunused),,-Wunused -Wextra) \ $(if $($(*F)_no_Wstack_usage),,$(STACK_USAGE_WARNING)) \ - $(if $($(*F)_no_Wpacked_not_aligned),-Wno-packed-not-aligned,) \ + $(if $($(*F)_no_Wpacked_not_aligned),$(NO_PACKED_NOT_ALIGNED_WARNING),) \ $($(*F)_CXXFLAGS) COMPILE.os = $(filter-out -fprofile-arcs -ftest-coverage, $(COMPILE)) diff --git a/configure.ac b/configure.ac index 5f3321aa..aa8439e8 100644 --- a/configure.ac +++ b/configure.ac @@ -546,6 +546,15 @@ CFLAGS="$old_CFLAGS"]) AM_CONDITIONAL(HAVE_TRAMPOLINES_WARNING, [test "x$ac_cv_trampolines" != "xno"]) +AC_CACHE_CHECK([whether the compiler accepts -Wno-packed-not-aligned], ac_cv_no_packed_not_aligned, [dnl +old_CFLAGS="$CFLAGS" +CFLAGS="$CFLAGS -Wno-packed-not-aligned -Werror" +AC_COMPILE_IFELSE([AC_LANG_SOURCE([])], + ac_cv_no_packed_not_aligned=yes, ac_cv_no_packed_not_aligned=no) +CFLAGS="$old_CFLAGS"]) +AM_CONDITIONAL(HAVE_NO_PACKED_NOT_ALIGNED_WARNING, + [test "x$ac_cv_no_packed_not_aligned" != "xno"]) + saved_LIBS="$LIBS" AC_SEARCH_LIBS([argp_parse], [argp]) LIBS="$saved_LIBS" -- 2.26.2 ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 3/3] build: Check for -Wno-packed-not-aligned support 2021-02-17 9:27 ` [PATCH 3/3] build: Check for -Wno-packed-not-aligned support tbaeder @ 2021-03-06 2:17 ` Mark Wielaard 0 siblings, 0 replies; 6+ messages in thread From: Mark Wielaard @ 2021-03-06 2:17 UTC (permalink / raw) To: tbaeder, elfutils-devel Hi Timm, On Wed, 2021-02-17 at 10:27 +0100, Timm Bäder via Elfutils-devel wrote: > From: Timm Bäder <tbaeder@redhat.com> > > Clang does not support this warning, so check for compiler support > before using it. It is somewhat unfortunate that we need to check for -Wno- acceptance with clang. gcc also doesn't support this warning in all versions, in the versions that do, it is enabled by -Wall. gcc -Wno-foobarbaz however is always accepted. The idea is that it is easy to not warn for something, even if you don't know what something is :) Anyway, if it is necessary for some compilers then lets add the extra check. Added ChangeLog entries and pushed. Cheers, Mark ^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately 2021-02-17 9:27 [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately tbaeder 2021-02-17 9:27 ` [PATCH 2/3] build: Check for -Wtrampolines support tbaeder 2021-02-17 9:27 ` [PATCH 3/3] build: Check for -Wno-packed-not-aligned support tbaeder @ 2021-03-06 1:25 ` Mark Wielaard 2 siblings, 0 replies; 6+ messages in thread From: Mark Wielaard @ 2021-03-06 1:25 UTC (permalink / raw) To: tbaeder, elfutils-devel Hi Timm, On Wed, 2021-02-17 at 10:27 +0100, Timm Bäder via Elfutils-devel wrote: > GCC accepts the =5, which means it doesn't try to parse any comments > and only accepts the fallthrough attribute in code. Clang does not ever > parse any comments and always wants the fallthrough attribute anyway. > Clang also doesn't accept the =n parameter for -Wimplicit-fallthrough. > > Test for =5 separately and use it if supported and fall back to just > -Wimplicit-fallthrough otherwise. Looks good, pushed. Thanks, Mark ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2021-03-06 2:17 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2021-02-17 9:27 [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately tbaeder 2021-02-17 9:27 ` [PATCH 2/3] build: Check for -Wtrampolines support tbaeder 2021-03-06 2:07 ` Mark Wielaard 2021-02-17 9:27 ` [PATCH 3/3] build: Check for -Wno-packed-not-aligned support tbaeder 2021-03-06 2:17 ` Mark Wielaard 2021-03-06 1:25 ` [PATCH 1/3] build: Check for -Wimplicit-fallthrough=5 separately Mark Wielaard
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