[review v3] Fix unused function error

["Pedro Alves (Code Review)" <gerrit@gnutoolchain-gerrit.osci.io>]

Pedro Alves has posted comments on this change.

Change URL: https://gnutoolchain-gerrit.osci.io/r/c/binutils-gdb/+/753
......................................................................


Patch Set 3:

(1 comment)

| --- /dev/null
| +++ /COMMIT_MSG
| @@ -1,0 +1,30 @@ 
| +Parent:     1d61b032 (Remove more shifts for sign/zero extension)
| +Author:     Luis Machado <luis.machado@linaro.org>
| +AuthorDate: 2019-12-11 11:55:49 -0300
| +Commit:     Luis Machado <luis.machado@linaro.org>
| +CommitDate: 2019-12-11 14:06:52 -0300
| +
| +Fix unused function error
| +
| +Attempting to build GDB in Ubuntu 16.04.6 LTS on x86_64, I ran into warnings
| +that caused the build to fail:
| +
| +binutils-gdb/gdb/gdbsupport/safe-strerror.c:44:1: error: ‘char* select_strerror_r(char*, char*)’ defined but not used [-Werror=unused-function]  select_strerror_r (char *res, char *)
| +
| +The diagnostics macros seem to expand correctly to their respective pragmas,
| +but it doesn't seem to have an effect on the warning. I tried to use the
| +pragmas explicitly and got the same result.
| +
| +ATTRIBUTE_UNUSED works fine in this case, if you put it in both functions,
| +which should fix warnings for both gdb and gdbserver builds.
| +
| +The compiler version is gcc (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609.

PS3, Line 21:

If this is legitimately a GCC bug, then I see two choices:

#1 - adjust to DIAGNOSTIC_IGNORE_UNUSED_FUNCTION to ignore "-Wunused"
instead of "-Wunused-function" for buggy gcc versions, assuming that
works.

#2 - switch to ATTRIBUTE_UNUSED like you have, but then we should nuke
DIAGNOSTIC_IGNORE_UNUSED_FUNCTION, since it doesn't work as
advertised.

ATTRIBUTE_UNUSED on the function like you have seems simpler for not
having to push/pop, aka not requiring global context.  So I'm fine
with option #2.

What doesn't look good to me is working around one case but letting
the bug latent for another user of DIAGNOSTIC_IGNORE_UNUSED_FUNCTION.
There's no other user of DIAGNOSTIC_IGNORE_UNUSED_FUNCTION currently,
AFAICS, so #2 should be trivial.

| +
| +gdb/ChangeLog:
| +
| +2019-12-11  Luis Machado  <luis.machado@linaro.org>
| +
| +	* gdb/gdbsupport/safe-strerror.c: Remove diagnostics.h
| +	(select_strerror_r): Use ATTRIBUTE_UNUSED instead of the diagnostics
| +	macros.
| +

-- 
Gerrit-Project: binutils-gdb
Gerrit-Branch: master
Gerrit-Change-Id: Iad6123d61d76d111e3ef8d24aa8c60112304c749
Gerrit-Change-Number: 753
Gerrit-PatchSet: 3
Gerrit-Owner: Luis Machado <luis.machado@linaro.org>
Gerrit-Reviewer: Luis Machado <luis.machado@linaro.org>
Gerrit-CC: Pedro Alves <palves@redhat.com>
Gerrit-Comment-Date: Wed, 11 Dec 2019 17:17:43 +0000
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