[PATCH] W/ Clang, compile C/C++ testcases with -Wno-unknown-warning-option
Pedro Alves
palves@redhat.com
Wed Jun 17 19:53:09 GMT 2020
On 6/17/20 6:29 PM, Gary Benson via Gdb-patches wrote:
> Pedro Alves wrote:
>> In general, the problematic sequence is something like this:
>>
>> #1 - A testcase compiles successfully with clang version X.
>> #2 - clang version "X + 1" adds a new warning, enabled by default,
>> which breaks the test.
>> #3 - We add -Wno-newwarning, fixing the testcase with clang "X + 1"
>> #4 - Now building the test with clang version X no longer works,
>> due to "unknown warning option".
>>
>> Making gcc_compile always add -Wno-unknown-warning-option to the
>> build flags fixes this problem for good. At least with clang.
>
> Right.
>
> First, I'm assuming you mean gdb_compile, not gcc_compile?
Yes.
>
> Second, it's not clear whether you mean to add it always, or just
> if the compiler is clang?
For Clang.
>
> Third, is this something you could easily do? Because I've spent
> nearly an hour on this already, gdb_compile is nearly 250 lines of
> special cases and I'm no closer to figuring out where I wouldn't
> break something.
Sure. Like this.
I tried adding -Wno-foo to a testcase and checked that without
the patch it failed due to the "unknown option" warning, and
passed with the patch.
>From 79f1cfddeea957a778c856c879a386901a96609b Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Wed, 17 Jun 2020 19:29:37 +0100
Subject: [PATCH] W/ Clang, compile C/C++ testcases with
-Wno-unknown-warning-option
Some C/C++ testcases unconditionally pass -Wno-foo as additional
options to disable some warning. That is OK with GCC, because GCC
accepts -Wno-foo silently even if it doesn't support -Wfoo. This is a
feature which allows disabling warnings with newer compilers without
breaking builds with older compilers. Clang however warns about
unknown -Wno-foo by default, unless you pass
-Wno-unknown-warning-option as well:
$ gcc -Wno-foo test.c
* nothing, compiles successfuly *
$ clang -Wno-foo test.c
warning: unknown warning option '-Wno-foo [-Wunknown-warning-option]
This commit adds -Wunknown-warning-option centrally in gdb_compile, so
that individual testcases don't have to worry about breaking older
Clangs.
IOW, this avoids this problematic scenario:
#1 - A testcase compiles successfully with Clang version X.
#2 - Clang version "X + 1" adds a new warning, enabled by default,
which breaks the test.
#3 - We add -Wno-newwarning to the testcase, fixing the testcase with
clang "X + 1".
#4 - Now building the test with Clang version X no longer works, due
to "unknown warning option".
gdb/testsuite/ChangeLog:
yyyy-mm-dd Pedro Alves <palves@redhat.com>
* lib/gdb.exp (gdb_compile): Update intro comment. If C/C++ with
Clang, add "-Wno-unknown-warning-option" to the options.
---
gdb/testsuite/lib/gdb.exp | 19 ++++++++++++++++++-
1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index f502eb157d8..bbc940a4512 100644
--- a/gdb/testsuite/lib/gdb.exp
+++ b/gdb/testsuite/lib/gdb.exp
@@ -3826,7 +3826,8 @@ set gdb_saved_set_unbuffered_mode_obj ""
# - ldflags=flag: Add FLAG to the linker flags.
# - incdir=path: Add PATH to the searched include directories.
# - libdir=path: Add PATH to the linker searched directories.
-# - ada, c++, f77: Compile the file as Ada, C++ or Fortran.
+# - ada, c++, f77, f90, rust: Compile the file as Ada, C++,
+# Fortran 77, Fortran 90 or Rust.
# - debug: Build with debug information.
# - optimize: Build with optimization.
@@ -3850,6 +3851,22 @@ proc gdb_compile {source dest type options} {
set new_options [universal_compile_options]
}
+ # Some C/C++ testcases unconditionally pass -Wno-foo as additional
+ # options to disable some warning. That is OK with GCC, because
+ # by design, GCC accepts any -Wno-foo option, even if it doesn't
+ # support -Wfoo. Clang however warns about unknown -Wno-foo by
+ # default, unless you pass -Wno-unknown-warning-option as well.
+ # We do that here, so that individual testcases don't have to
+ # worry about it.
+ if {[lsearch -exact $options getting_compiler_info] == -1
+ && [lsearch -exact $options rust] == -1
+ && [lsearch -exact $options ada] == -1
+ && [lsearch -exact $options f77] == -1
+ && [lsearch -exact $options f90] == -1
+ && [test_compiler_info "clang-*"]} {
+ lappend new_options "additional_flags=-Wno-unknown-warning-option"
+ }
+
# Place (and look for) Fortran `.mod` files in the output
# directory for this specific test.
if {[lsearch -exact $options f77] != -1 \
base-commit: 669203174311c5be76744a879563c697cd479853
--
2.14.5
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