Re: [PATCH] W/ Clang, compile C/C++ testcases with -Wno-unknown-warning-option

[Pedro Alves <palves@redhat.com>]

On 6/18/20 5:18 PM, Gary Benson via Gdb-patches wrote:
> Pedro Alves wrote:
>> 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
> 
> Oh, thanks, that looks great.  Could you commit it please?

I've pushed this now, with just a tweak to also list "go".

From 331733cd4e2f2fe76c0b7b6fdd81e54724572354 Mon Sep 17 00:00:00 2001
From: Pedro Alves <palves@redhat.com>
Date: Wed, 24 Jun 2020 23:18:19 +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:
2020-06-24  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/ChangeLog   |  5 +++++
 gdb/testsuite/lib/gdb.exp | 20 +++++++++++++++++++-
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 26284dabb25..6f4d99d3902 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2020-06-24  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.
+
 2020-06-23  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.xml/tdesc-reload.c: New file.
diff --git a/gdb/testsuite/lib/gdb.exp b/gdb/testsuite/lib/gdb.exp
index 7b243f5fff3..6b4f71be588 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, go, rust: Compile the file as Ada, C++,
+#     Fortran 77, Fortran 90, Go or Rust.
 #   - debug: Build with debug information.
 #   - optimize: Build with optimization.
 
@@ -3850,6 +3851,23 @@ 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
+	&& [lsearch -exact $options go] == -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: a8654e7d784980cb4596f685964200fcc1164c78
-- 
2.14.5