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Re: [PATCH] gdb: Fix build error on macOS
From: |
Bruno Haible |
Subject: |
Re: [PATCH] gdb: Fix build error on macOS |
Date: |
Wed, 06 Oct 2021 02:05:39 +0200 |
Enze Li wrote:
> > PR build/28413 notes that the gdb master fails to build on macOS.
The build fails due to the combination of '-Werror' and a useful
warning emitted by Gnulib.
But Gnulib does not support '-Werror'. To fix the issue, you need to
filter out the '-Werror' option. Or not add it in the first place.
> > Based on De Morgan's law, the expression
> > !(defined __GNUC__ && !defined __clang__ && __OPTIMIZE__)
> > is equal to (!defined __GNUC__ || defined __clang__ || !__OPTIMIZE).
> > The expression above looks weird, maybe there are some problems with
> > this way of judging. When any one of the conditions is established, the
> > subsequent judgment will be ignored.
> >
> > This patch works around the issue by rewriting the expression of
> > judgment after referring to the nearby notes.
This text does not explain what the patch does.
> > --- a/gnulib/import/c++defs.h
> > +++ b/gnulib/import/c++defs.h
> > @@ -286,7 +286,7 @@
> > _GL_CXXALIASWARN_2 (func, namespace)
> > /* To work around GCC bug
> > <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
> > we enable the warning only when not optimizing. */
> > -# if !(defined __GNUC__ && !defined __clang__ && __OPTIMIZE__)
> > +# if defined __GNUC__ && !defined __clang__ && !__OPTIMIZE__
> > # define _GL_CXXALIASWARN_2(func,namespace) \
> > _GL_WARN_ON_USE (func, \
> > "The symbol ::" #func " refers to the system
> > function. " \
The previous code enables a useful warning for clang, and does not enable it
for GCC because that would trigger a GCC bug.
Your patch swaps the cases of clang and GCC. Thus it removes a useful warning
for clang builds, and triggers a known GCC bug in the GCC builds.
> > @@ -314,7 +314,7 @@
> > _GL_CXXALIASWARN1_2 (func, rettype, parameters_and_attributes,
> > namespace)
> > /* To work around GCC bug
> > <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43881>,
> > we enable the warning only when not optimizing. */
> > -# if !(defined __GNUC__ && !defined __clang__ && __OPTIMIZE__)
> > +# if defined __GNUC__ && !defined __clang__ && !__OPTIMIZE__
> > # define
> > _GL_CXXALIASWARN1_2(func,rettype,parameters_and_attributes,namespace) \
> > _GL_WARN_ON_USE_CXX (func, rettype, rettype,
> > parameters_and_attributes, \
> > "The symbol ::" #func " refers to the system
> > function. " \
Likewise.
So, the patch is bad on all accounts.
Bruno