Re: Warnings in mingw64 builds on master

[Andy Moreton <andrewjmoreton@gmail.com>]

On Sat 15 Aug 2020, Eli Zaretskii wrote:

>> From: Andy Moreton <andrewjmoreton@gmail.com>
>> Date: Fri, 14 Aug 2020 23:37:27 +0100
>> 
>> Building master for 64bit mingw64 gives the following warnings:
>> 
>> C:/emacs/git/emacs/master/src/w32reg.c:146:1: warning: function might be
>> candidate for attribute 'malloc' [-Wsuggest-attribute=malloc]
>>   146 | w32_get_string_resource (void *v_rdb, const char *name, const char *class)
>>       | ^~~~~~~~~~~~~~~~~~~~~~~
>
> That's just noise.  There's nothing wrong with the code.

Agreed. However it is better to have a clean build than to have
pointless warnings, so the real errors stand out.

>> C:/emacs/git/emacs/master/src/w32menu.c: In function 'set_frame_menubar':
>> C:/emacs/git/emacs/master/src/w32menu.c:326:2: warning: 'memcpy' offset [3,
>> 10] from the object at '<unknown>' is out of the bounds of referenced
>> subobject 'contents' with type 'union Lisp_X *[]' at offset 3
>> [-Warray-bounds]
>>   326 |  memcpy (previous_items, XVECTOR (f->menu_bar_vector)->contents,
>>       |  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>   327 |   previous_menu_items_used * word_size);
>>       |   ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>> In file included from C:/emacs/git/emacs/master/src/w32menu.c:26:
>> C:/emacs/git/emacs/master/src/lisp.h:1631:17: note: subobject 'contents' declared here
>>  1631 |     Lisp_Object contents[FLEXIBLE_ARRAY_MEMBER];
>>       |                 ^~~~~~~~
>
> Likewise.
>
>> C:/emacs/git/emacs/master/src/w32.c: In function '_sys_read_ahead':
>> C:/emacs/git/emacs/master/src/w32.c:8785:10: warning: 'rc' may be used uninitialized in this function [-Wmaybe-uninitialized]
>>  8785 |   if (rc == sizeof (char))
>>       |       ~~~^~~~~~~~~~~~~~~~
>
> This is a bug in the compiler you are using: rc _is_ initialized.

The is "gcc version 10.2.0 (Rev1, Built by MSYS2 project)" so not
exactly old. More silly warnings that it would be better to disable.


>> C:/emacs/git/emacs/master/src/image.c:116: warning: macro "PIX_MASK_DRAW" is not used [-Wunused-macros]
>>   116 | #define PIX_MASK_DRAW 1
>>       | 
>
> This macro is used in the PNG code.  Are you building without PNG
> support?

Yes, as the native image support handles PNG.

>> These must have been introduced fairly recently, as the build was clean
>> earlier this year.
>
> Actually, this code was not touched in years, so I'm guessing you
> upgraded to a later version of the compiler lately.

Yes - it is whatever is current in in the MSYS distro. 

    AndyM