Re: pkg/32097

[segv%netctl.net@localhost]

The following reply was made to PR pkg/32097; it has been noted by GNATS.

From: segv%netctl.net@localhost
To: gnats-bugs%NetBSD.org@localhost
Cc: grant%NetBSD.org@localhost
Subject: Re: pkg/32097
Date: Fri, 18 Nov 2005 00:37:39 +0000

 OK dudes, I found the problem, it is in libnbcompat/vis.c file
 
 It has the following macro:
 
 #define MAKEEXTRALIST(flag, extra, orig)                                      \
 do {                                                                          \
         const char *o = orig;                                                 \
         char *e;                                                              \
         while (*o++)                                                          \
                 continue;                                                     \
         extra = alloca((size_t)((o - orig) + MAXEXTRAS));                     \
         for (o = orig, e = extra; (*e++ = *o++) != '\0';)                     \
                 continue;                                                     \
         e--;                                                                  \
         if (flag & VIS_SP) *e++ = ' ';                                        \
         if (flag & VIS_TAB) *e++ = '\t';                                      \
         if (flag & VIS_NL) *e++ = '\n';                                       \
         if ((flag & VIS_NOSLASH) == 0) *e++ = '\\';                           \
         *e = '\0';                                                            \
 } while (/*CONSTCOND*/0)
 
 
 and then later in the file the macro is called in the following way:
 
 MAKEEXTRALIST(flag, extra, "");
 
 the third argument to the macro causes problems, because it expands to empty
 string constants, which are stored at different addresses, so on a big-endian
 sparc machine:
 
 extra = alloca((size_t)((o - orig) + MAXEXTRAS));
 
 calls alloca() funcation, passing it a huge number, which overruns the stack
 and crashes the program.
 
 Below you can see the different behaviour you get with different compilers
 
 [ultra10] cat test.c
 #include <stdio.h>
 
 int main(void) 
 {
         printf("%lu\n", "" - "");
 }
 [ultra10] gcc test.c
 [ultra10] ./a.out
 0
 [ultra10] /opt/SUNWspro/bin/cc test.c
 [ultra10] ./a.out
 4294967292
 [ultra10]
 
 
 So, somebody has to fix vis.c file
 
 --- vis.c.orig  Fri Nov 18 00:16:26 2005
 +++ vis.c       Fri Nov 18 00:23:35 2005
 @@ -329,10 +329,11 @@
  
  {
         char *extra;
 +       const char *emptystr = "";
  
         _DIAGASSERT(dst != NULL);
  
 -       MAKEEXTRALIST(flag, extra, "");
 +       MAKEEXTRALIST(flag, extra, emptystr);
         if (flag & VIS_HTTPSTYLE)
                 HVIS(dst, c, flag, nextc, extra);
         else
 @@ -359,8 +360,9 @@
         int flag;
  {
         char *extra;
 +       const char *emptystr = "";
  
 -       MAKEEXTRALIST(flag, extra, "");
 +       MAKEEXTRALIST(flag, extra, emptystr);
         return (strsvis(dst, src, flag, extra));
  }
  
 @@ -373,7 +375,8 @@
         int flag;
  {
         char *extra;
 +       const char *emptystr = "";
  
 -       MAKEEXTRALIST(flag, extra, "");
 +       MAKEEXTRALIST(flag, extra, emptystr);
         return (strsvisx(dst, src, len, flag, extra));
  }