warnings in win32 builds from trunk

warnings in win32 builds from trunk

[Corwin Brust]

Attempting to build a snapshot from the master branch today I noticed
some warnings.  Here they are; please let me know if there's else I
might helpfully do to troubleshoot/debug these (e.g. open a bug
report).

Maybe easier to read:
  https://bpa.st/6EBA

Inline (to EOM):

  CC       w32notify.o
In file included from C:/Users/corwi/emacs-build/git/master/src/process.c:33:
C:/Users/corwi/emacs-build/git/master/src/process.c: In function
'Fmake_process':
C:/Users/corwi/emacs-build/git/master/src/lisp.h:1649:31: warning:
null pointer dereference [-Wnull-dereference]
 1649 |   return XSTRING (string)->u.s.data;
      |          ~~~~~~~~~~~~~~~~~~~~~^~~~~
  CC       profiler.o
  CC       decompress.o
  CC       thread.o
  CC       systhread.o
  CC       sqlite.o
  CC       hbfont.o
  CC       w32fns.o
  CC       w32menu.o
  CC       w32reg.o
  CC       w32font.o
  CC       w32term.o
  CC       w32xfns.o
  CC       w32select.o
  CC       w32uniscribe.o
  CC       w32cygwinx.o
  CC       w32.o
  CC       w32console.o
  CC       w32heap.o
  CC       w32inevt.o
  CC       w32proc.o
  CC       w32image.o
  CC       fontset.o
  CC       fringe.o
  CC       image.o
C:/Users/corwi/emacs-build/git/master/src/w32menu.c: In function
'set_frame_menubar':
C:/Users/corwi/emacs-build/git/master/src/w32menu.c:324:9: warning:
'memcpy' offset [3, 10] from the object at '<unknown>' is out of the
bounds of referenced subobject 'contents' with type 'struct Lisp_X
*[]' at offset 3 [-Warray-bounds]
  324 |         memcpy (previous_items, XVECTOR (f->menu_bar_vector)->contents,
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  325 |                 previous_menu_items_used * word_size);
      |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from C:/Users/corwi/emacs-build/git/master/src/w32menu.c:26:
C:/Users/corwi/emacs-build/git/master/src/lisp.h:1725:17: note:
subobject 'contents' declared here
 1725 |     Lisp_Object contents[FLEXIBLE_ARRAY_MEMBER];
      |                 ^~~~~~~~
C:/Users/corwi/emacs-build/git/master/src/w32heap.c: In function 'getrlimit':
C:/Users/corwi/emacs-build/git/master/src/w32heap.c:853:14: warning:
'm' may be used uninitialized [-Wmaybe-uninitialized]
  853 |         if (!VirtualQuery ((LPCVOID) &m, &m, sizeof m))
      |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from C:/msys2/mingw64/x86_64-w64-mingw32/include/winbase.h:25,
                 from C:/msys2/mingw64/x86_64-w64-mingw32/include/windows.h:70,
                 from C:/Users/corwi/emacs-build/git/master/src/w32common.h:24,
                 from C:/Users/corwi/emacs-build/git/master/src/w32heap.c:54:
C:/msys2/mingw64/x86_64-w64-mingw32/include/memoryapi.h:45:28: note:
by argument 1 of type 'LPCVOID' {aka 'const void *'} to 'VirtualQuery'
declared here
   45 |   WINBASEAPI SIZE_T WINAPI VirtualQuery (LPCVOID lpAddress,
PMEMORY_BASIC_INFORMATION lpBuffer, SIZE_T dwLength);
      |                            ^~~~~~~~~~~~
C:/Users/corwi/emacs-build/git/master/src/w32heap.c:844:34: note: 'm'
declared here
  844 |         MEMORY_BASIC_INFORMATION m;
      |                                  ^
  CC       json.o
  CC       tparam.o

Re: warnings in win32 builds from trunk

[Eli Zaretskii]

> From: Corwin Brust <corwin@bru.st>
> Date: Sat, 2 Apr 2022 18:33:27 -0500
> 
> Attempting to build a snapshot from the master branch today I noticed
> some warnings.  Here they are; please let me know if there's else I
> might helpfully do to troubleshoot/debug these (e.g. open a bug
> report).

Please file a bug report for each one of them.

> In file included from C:/Users/corwi/emacs-build/git/master/src/process.c:33:
> C:/Users/corwi/emacs-build/git/master/src/process.c: In function
> 'Fmake_process':
> C:/Users/corwi/emacs-build/git/master/src/lisp.h:1649:31: warning:
> null pointer dereference [-Wnull-dereference]
>  1649 |   return XSTRING (string)->u.s.data;
>       |          ~~~~~~~~~~~~~~~~~~~~~^~~~~

Line 1649 of lisp.h is inside SDATA.  But since Fmake_process doesn't
call SDATA directly, I don't know which string object is this about.
(Really, the compiler should do a better job when reporting such
issues, by showing all the relevant source locations.)

> C:/Users/corwi/emacs-build/git/master/src/w32menu.c: In function
> 'set_frame_menubar':
> C:/Users/corwi/emacs-build/git/master/src/w32menu.c:324:9: warning:
> 'memcpy' offset [3, 10] from the object at '<unknown>' is out of the
> bounds of referenced subobject 'contents' with type 'struct Lisp_X
> *[]' at offset 3 [-Warray-bounds]
>   324 |         memcpy (previous_items, XVECTOR (f->menu_bar_vector)->contents,
>       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   325 |                 previous_menu_items_used * word_size);
>       |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> In file included from C:/Users/corwi/emacs-build/git/master/src/w32menu.c:26:
> C:/Users/corwi/emacs-build/git/master/src/lisp.h:1725:17: note:
> subobject 'contents' declared here
>  1725 |     Lisp_Object contents[FLEXIBLE_ARRAY_MEMBER];
>       |                 ^~~~~~~~

This is some general problem with FLEXIBLE_ARRAY_MEMBER, not specific
to w32.  Sounds like latest compilers don't like that.  Are you
building with custom compiler switches, per chance?

> C:/Users/corwi/emacs-build/git/master/src/w32heap.c: In function 'getrlimit':
> C:/Users/corwi/emacs-build/git/master/src/w32heap.c:853:14: warning:
> 'm' may be used uninitialized [-Wmaybe-uninitialized]
>   853 |         if (!VirtualQuery ((LPCVOID) &m, &m, sizeof m))
>       |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

This is a bogus warning, ignore it.  The compiler doesn't understand
the semantics of VirtualQuery.

Thanks.

Re: warnings in win32 builds from trunk

[Corwin Brust]

On Sun, Apr 3, 2022 at 1:17 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Corwin Brust <corwin@bru.st>
> > Date: Sat, 2 Apr 2022 18:33:27 -0500
> >
> > Attempting to build a snapshot from the master branch today I noticed
> > some warnings.  Here they are; please let me know if there's else I
> > might helpfully do to troubleshoot/debug these (e.g. open a bug
> > report).
>
> Please file a bug report for each one of them.

Now done (except for the one you indicated should be ignored).

Replying here also in case that's helpful for posterity; see detail below.

>
> > In file included from C:/Users/corwi/emacs-build/git/master/src/process.c:33:
> > C:/Users/corwi/emacs-build/git/master/src/process.c: In function
> > 'Fmake_process':
> > C:/Users/corwi/emacs-build/git/master/src/lisp.h:1649:31: warning:
> > null pointer dereference [-Wnull-dereference]
> >  1649 |   return XSTRING (string)->u.s.data;
> >       |          ~~~~~~~~~~~~~~~~~~~~~^~~~~
>
> Line 1649 of lisp.h is inside SDATA.  But since Fmake_process doesn't
> call SDATA directly, I don't know which string object is this about.
> (Really, the compiler should do a better job when reporting such
> issues, by showing all the relevant source locations.)

bug#54695: 29.0.50; w32notify.o Fmake_process warning building on win32

>
> > C:/Users/corwi/emacs-build/git/master/src/w32menu.c: In function
> > 'set_frame_menubar':
> > C:/Users/corwi/emacs-build/git/master/src/w32menu.c:324:9: warning:
> > 'memcpy' offset [3, 10] from the object at '<unknown>' is out of the
> > bounds of referenced subobject 'contents' with type 'struct Lisp_X
> > *[]' at offset 3 [-Warray-bounds]
> >   324 |         memcpy (previous_items, XVECTOR (f->menu_bar_vector)->contents,
> >       |         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   325 |                 previous_menu_items_used * word_size);
> >       |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > In file included from C:/Users/corwi/emacs-build/git/master/src/w32menu.c:26:
> > C:/Users/corwi/emacs-build/git/master/src/lisp.h:1725:17: note:
> > subobject 'contents' declared here
> >  1725 |     Lisp_Object contents[FLEXIBLE_ARRAY_MEMBER];
> >       |                 ^~~~~~~~
>
> This is some general problem with FLEXIBLE_ARRAY_MEMBER, not specific
> to w32.  Sounds like latest compilers don't like that.  Are you
> building with custom compiler switches, per chance?

bug#54694: 29.0.50; w32menu.o set_frame_menubar warning building on win32

I don't think I am building with any custom compiler switches.

Configured using:
 'configure --without-dbus --with-native-compilation
 --without-compress-install -C 'CFLAGS=-O2 -g3''

Configured features:
ACL GIF GMP GNUTLS HARFBUZZ JPEG JSON LCMS2 LIBXML2 MODULES NATIVE_COMP
NOTIFY W32NOTIFY PDUMPER PNG RSVG SOUND SQLITE3 THREADS TIFF
TOOLKIT_SCROLL_BARS WEBP XPM ZLIB

>
> > C:/Users/corwi/emacs-build/git/master/src/w32heap.c: In function 'getrlimit':
> > C:/Users/corwi/emacs-build/git/master/src/w32heap.c:853:14: warning:
> > 'm' may be used uninitialized [-Wmaybe-uninitialized]
> >   853 |         if (!VirtualQuery ((LPCVOID) &m, &m, sizeof m))
> >       |              ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
> This is a bogus warning, ignore it.  The compiler doesn't understand
> the semantics of VirtualQuery.

So I didn't create a bug report for this one.  Please LMK if it's
helpful for me to do so.

>
> Thanks.