Re: [Emacs-diffs] master 0c94b84: * nt/inc/ms-w32.h (execve) [MINGW_W64]: Make commentary more accurate.

[Angelo Graziosi <angelo.graziosi@alice.it>]

Hi Paul,

Il 02/09/2016 08:53, Eli Zaretskii ha scritto:
>> From: Ken Brown <kbrown@cornell.edu>
>> Cc: Angelo Graziosi <angelo.graziosi@alice.it>
>> Date: Thu, 1 Sep 2016 15:57:00 -0400
>>
>> On 9/1/2016 1:16 PM, Eli Zaretskii wrote:
>>> +   However, using the prototype with intptr_t causes GCC to emit
>>> +   warnings.  Fortunately, execve is not used in the MinGW build, but
>>> +   the code that references it is still compiled.  */
>>
>> Wouldn't it be easier to prevent that code from being compiled?
>
> It would for the Windows build, but it would add one (actually more,
> see below) #ifdef WINDOWSNT into the mainline code.  AFAIR, Paul
> (CC'ed) wanted to keep those to a minimum, so I preferred not to ifdef
> away the code.

if I understand (in short) there is code compiled but not used.. Would 
it better to exclude that code as Ken suggests, then?

May you comment?

Thanks,
  Angelo.

>
>> I think the following would suffice:
>>
>> --- a/src/sysdep.c
>> +++ b/src/sysdep.c
>> @@ -146,6 +146,7 @@ disable_address_randomization (void)
>>   }
>>   #endif
>>
>> +#ifndef WINDOWSNT
>>   /* Execute the program in FILE, with argument vector ARGV and environ
>>      ENVP.  Return an error number if unsuccessful.  This is like execve
>>      except it reenables ASLR in the executed program if necessary, and
>> @@ -170,6 +171,7 @@ emacs_exec_file (char const *file, char *const
>> *argv, char *const *envp)
>>
>>     return err;
>>   }
>> +#endif /* not WINDOWSNT */
>
> That whole function is not used on Windows, so if we are to do this,
> the following fragment of main in emacs.c should also be ifdefed away:
>
>     /* True if address randomization interferes with memory allocation.  */
>   # ifdef __PPC64__
>     bool disable_aslr = true;
>   # else
>     bool disable_aslr = dumping;
>   # endif
>
>     if (disable_aslr && disable_address_randomization ())
>       {
> 	/* Set this so the personality will be reverted before execs
> 	   after this one.  */
> 	xputenv ("EMACS_HEAP_EXEC=true");
>
> 	/* Address randomization was enabled, but is now disabled.
> 	   Re-execute Emacs to get a clean slate.  */
> 	execvp (argv[0], argv);
>
> 	/* If the exec fails, warn and then try anyway.  */
> 	perror (argv[0]);
>       }
>
> If Paul doesn't mind (nor anyone else), we can certainly do that.
>
> Thanks.
>