[MacPorts] #69384: gklib @20230327: error: 'lnlen' may be used uninitialized in this function (was: gklib fails on 10.5 PPC)

[MacPorts]

#69384: gklib @20230327: error: 'lnlen' may be used uninitialized in this function
-----------------------+---------------------------------------
  Reporter:  rmottola  |      Owner:  catap
      Type:  defect    |     Status:  assigned
  Priority:  Normal    |  Milestone:
 Component:  ports     |    Version:
Resolution:            |   Keywords:  tiger leopard snowleopard
      Port:  gklib     |
-----------------------+---------------------------------------
Changes (by ryandesign):

 * keywords:  leopard  gcc => tiger leopard snowleopard


Comment:

 Please attach the main.log file.

 I am not able to reproduce the problem on macOS 12 building using Xcode
 clang or MacPorts gcc 13. I can't test gcc 7 because it's too old for this
 OS.

 Replying to [ticket:69384 rmottola]:
 > {{{
 > io.c: In function 'gk_readfile':
 > io.c:113:24: error: 'lnlen' may be used uninitialized in this function
 [-Werror=maybe-uninitialized]
 >    if (*lineptr == NULL || *n == 0) {
 >        ~~~~~~~~~~~~~~~~~^~~~~~~~~~
 > }}}

 `gk_readfile` uses `lnlen` only once, at the end of this chunk:

 https://github.com/KarypisLab/GKlib/blob/8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c#L147-L159

 {{{#!c
 char **gk_readfile(char *fname, size_t *r_nlines)
 {
   size_t lnlen, nlines=0;
   char *line=NULL, **lines=NULL;
   FILE *fpin;

   gk_getfilestats(fname, &nlines, NULL, NULL, NULL);
   if (nlines > 0) {
     lines = (char **)gk_malloc(nlines*sizeof(char *), "gk_readfile:
 lines");

     fpin = gk_fopen(fname, "r", "gk_readfile");
     nlines = 0;
     while (gk_getline(&line, &lnlen, fpin) != -1) {
 }}}

 As we see at the top of the function, at this point `line` is a `NULL`
 pointer and `lnlen` is uninitialized.

 `gk_getline` in turn does this:

 https://github.com/KarypisLab/GKlib/blob/8bd6bad750b2b0d90800c632cf18e8ee93ad72d7/io.c#L101C1-L116

 {{{#!c
 ssize_t gk_getline(char **lineptr, size_t *n, FILE *stream)
 {
 #ifdef HAVE_GETLINE
   return getline(lineptr, n, stream);
 #else
   size_t i;
   int ch;

   if (feof(stream))
     return -1;

   /* Initial memory allocation if *lineptr is NULL */
   if (*lineptr == NULL || *n == 0) {
     *n = 1024;
     *lineptr = gk_malloc((*n)*sizeof(char), "gk_getline: lineptr");
   }
 }}}

 The way I read this, in this call, `*lineptr` (aka `line`) is `NULL`, so
 the second part of the condition checking if `*n` (aka `lnlen` which is
 uninitialized) is `0` is not evaluated, so I don't think the variable is
 being used uninitialized. You could still report the problem to the
 developers; it would be simple to just initialize the variable anyway.

 `HAVE_GETLINE` is true on Mac OS X 10.7 or later, so this problem only
 affects Mac OS X 10.6 and earlier, which is probably why not more people
 have reported it.

 I tried removing these lines from GKlibSystem.cmake (because I could find
 no way to override this result on the command line):

 {{{
 check_function_exists(getline HAVE_GETLINE)
 if(HAVE_GETLINE)
   set(GKlib_COPTIONS "${GKlib_COPTIONS} -DHAVE_GETLINE")
 endif(HAVE_GETLINE)
 }}}

 Even so, I did not see a build error with Xcode clang or MacPorts gcc 13.
 Maybe this warning was improved in later GCC versions to be more accurate.

 The build system sets `-Werror` only when the compiler is GCC. I submitted
 a PR to stop doing that:

 https://github.com/KarypisLab/GKlib/pull/36

-- 
Ticket URL: <https://trac.macports.org/ticket/69384#comment:5>
MacPorts <https://www.macports.org/>
Ports system for macOS