[PATCH 0/13] v2 warning control by group and location (PR 74765)

[Martin Sebor]

On 7/17/21 2:36 PM, Jan-Benedict Glaw wrote:
> Hi Martin!
> 
> On Fri, 2021-06-04 15:27:04 -0600, Martin Sebor <msebor@gmail.com> wrote:
>> This is a revised patch series to add warning control by group and
>> location, updated based on feedback on the initial series.
> [...]
> 
> My automated checking (in this case: Using Debian's "gcc-snapshot"
> package) indicates that between versions 1:20210527-1 and
> 1:20210630-1, building GDB breaks. Your patch is a likely candidate.
> It's a case where a method asks for a nonnull argument and later on
> checks for NULLness again. The build log is currently available at
> (http://wolf.lug-owl.de:8080/jobs/gdb-vax-linux/5), though obviously
> breaks for any target:
> 
> configure --target=vax-linux --prefix=/tmp/gdb-vax-linux
> make all-gdb
> 
> [...]
> [all 2021-07-16 19:19:25]   CXX    compile/compile.o
> [all 2021-07-16 19:19:30] In file included from ./../gdbsupport/common-defs.h:126,
> [all 2021-07-16 19:19:30]                  from ./defs.h:28,
> [all 2021-07-16 19:19:30]                  from compile/compile.c:20:
> [all 2021-07-16 19:19:30] ./../gdbsupport/gdb_unlinker.h: In constructor 'gdb::unlinker::unlinker(const char*)':
> [all 2021-07-16 19:19:30] ./../gdbsupport/gdb_assert.h:35:4: error: 'nonnull' argument 'filename' compared to NULL [-Werror=nonnull-compare]
> [all 2021-07-16 19:19:30]    35 |   ((void) ((expr) ? 0 :                                                       \
> [all 2021-07-16 19:19:30]       |   ~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> [all 2021-07-16 19:19:30]    36 |            (gdb_assert_fail (#expr, __FILE__, __LINE__, FUNCTION_NAME), 0)))
> [all 2021-07-16 19:19:30]       |            ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> [all 2021-07-16 19:19:30] ./../gdbsupport/gdb_unlinker.h:38:5: note: in expansion of macro 'gdb_assert'
> [all 2021-07-16 19:19:30]    38 |     gdb_assert (filename != NULL);
> [all 2021-07-16 19:19:30]       |     ^~~~~~~~~~
> [all 2021-07-16 19:19:31] cc1plus: all warnings being treated as errors
> [all 2021-07-16 19:19:31] make[1]: *** [Makefile:1641: compile/compile.o] Error 1
> [all 2021-07-16 19:19:31] make[1]: Leaving directory '/var/lib/laminar/run/gdb-vax-linux/5/binutils-gdb/gdb'
> [all 2021-07-16 19:19:31] make: *** [Makefile:11410: all-gdb] Error 2
> 
> 
> Code is this:
> 
>   31 class unlinker
>   32 {
>   33  public:
>   34
>   35   unlinker (const char *filename) ATTRIBUTE_NONNULL (2)
>   36     : m_filename (filename)
>   37   {
>   38     gdb_assert (filename != NULL);
>   39   }
> 
> I'm quite undecided whether this is bad behavior of GCC or bad coding
> style in Binutils/GDB, or both.

A warning should be expected in this case.  Before the recent GCC
change it was inadvertently suppressed in gdb_assert macros by its
operand being enclosed in parentheses.

Martin

> 
> Thanks,
>    Jan-Benedict
>