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Subject: Re: gcc-7.1.0
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References: <6953e282-24aa-2b4e-2141-385d8b443111 AT iki DOT fi>
 <590A6154 DOT 8010308 AT gmx DOT de> <83a86shf9d DOT fsf AT gnu DOT org> <590BA4E2 DOT 4000406 AT gmx DOT de>
From: "Andris Pavenis (andris DOT pavenis AT iki DOT fi) [via djgpp-workers AT delorie DOT com]" <djgpp-workers AT delorie DOT com>
Message-ID: <49ae1668-e108-5e0b-350c-533d29574dba@iki.fi>
Date: Fri, 5 May 2017 07:12:11 +0300
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On 05/05/2017 01:02 AM, Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via djgpp-workers AT delorie DOT com] 
wrote:
> Am 04.05.2017 16:23, schrieb Eli Zaretskii (eliz AT gnu DOT org) [via djgpp-workers AT delorie DOT com]:
>>> Date: Thu, 04 May 2017 01:01:40 +0200
>>> From: "Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via 
>>> djgpp-workers AT delorie DOT com]"<djgpp-workers AT delorie DOT com>
> [snip]
>>
>> It's probably best to tweak the code to make sure the buffer overruns
>> cannot happen.
>
> I have tried to fix the buffer overruns by recomputing the length correctly
> so the compiler stops complaining.  Also some minor warnings in the zoneinfo
> code has been fixed but they do not stop compilation.  I have added "break"
> in switch statements where they are missed.  Neitherless there are some
> warnings due to intentional fall throughs that may be suppressed by excluding
> the corresponding compiler warning settings [-Wimplicit-fallthrough=].
>
> As usual suggestions, objections, comments are welcome.
>
>
> Regards,
> Juan M. Guerrero
>

I guess better way is to add explicit casts to unsigned short. Attached patch seems to be sufficient.
Tested however build only using Linux to DJGPP cross-compiler.

Andris



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Index: dosexec.c
===================================================================
RCS file: /cvs/djgpp/djgpp/src/libc/dos/process/dosexec.c,v
retrieving revision 1.27
diff -p -r1.27 dosexec.c
*** dosexec.c	2 May 2015 07:32:23 -0000	1.27
--- dosexec.c	5 May 2017 04:04:28 -0000
*************** direct_exec_tail_1 (const char *program,
*** 406,412 ****
    if ((initial_tbuf_selector != tbuf_selector) && proxy_off)
    {
      char temp[65], *s, t2[5];
!     sprintf (t2, "%04lX", tbuf_beg>>4);
      dosmemget (tbuf_beg+proxy_off, 64, temp);
      temp[64] = 0;
      s = strchr(temp,'\r');
--- 406,412 ----
    if ((initial_tbuf_selector != tbuf_selector) && proxy_off)
    {
      char temp[65], *s, t2[5];
!     sprintf (t2, "%04X", (unsigned short)(tbuf_beg>>4));
      dosmemget (tbuf_beg+proxy_off, 64, temp);
      temp[64] = 0;
      s = strchr(temp,'\r');
*************** static int go32_exec(const char *program
*** 1107,1115 ****
    proxy_cmdline = (char *)alloca (34);
    
    sprintf(proxy_cmdline, "%s=%04x %04x %04x %04x %04x",
!     __PROXY, argc,
!    (unsigned)(tbuf_beg >> 4), rm_off & 0xffff,
!    (unsigned)(tbuf_beg >> 4), si_off & 0xffff);
    if (!found_si)
      proxy_cmdline[22] = 0; /* remove stubinfo information */
  
--- 1107,1115 ----
    proxy_cmdline = (char *)alloca (34);
    
    sprintf(proxy_cmdline, "%s=%04x %04x %04x %04x %04x",
!     __PROXY, (unsigned short)argc,
!     (unsigned short)(tbuf_beg >> 4), (unsigned short)(rm_off & 0xffff),
!     (unsigned short)(tbuf_beg >> 4), (unsigned short)(si_off & 0xffff));
    if (!found_si)
      proxy_cmdline[22] = 0; /* remove stubinfo information */
  

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