Re: Bison fix to not generate a temporary file

[Hans Aberg]

At 00:39 -0700 2002/10/20, Paul Eggert wrote:
 static void
 output_skeleton (void)
 {
...
+  FILE *in;
+  FILE *out;
+  int filter_fd[2];
+  char const *argv[7];
+  pid_t pid;
+
+  /* Compute the names of the package data dir and skeleton file.
+     Test whether m4sugar.m4 is readable, to check for proper
+     installation.  A faulty installation can cause deadlock, so a
+     cheap sanity check is worthwhile.  */
+  char const m4sugar[] = "m4sugar/m4sugar.m4";
+  char *full_path;
+  char const *p;
+  char const *m4 = (p = getenv ("M4")) ? p : M4;
+  char const *pkgdatadir = (p = getenv ("BISON_PKGDATADIR")) ? p : PKGDATADIR;
+  size_t skeleton_size = strlen (skeleton) + 1;
+  size_t pkgdatadirlen = strlen (pkgdatadir);
+  while (pkgdatadirlen && pkgdatadir[pkgdatadirlen - 1] == '/')
+    pkgdatadirlen--;
+  full_path = xmalloc (pkgdatadirlen + 1
+                      + (skeleton_size < sizeof m4sugar
+                         ? sizeof m4sugar : skeleton_size));
+  strcpy (full_path, pkgdatadir);
+  full_path[pkgdatadirlen] = '/';
+  strcpy (full_path + pkgdatadirlen + 1, m4sugar);
+  in = fopen (full_path, "r");
+  if (! in || fclose (in) != 0)
+    error (EXIT_FAILURE, errno, "%s", full_path);
+  strcpy (full_path + pkgdatadirlen + 1, skeleton);
...

One other thing: Code that relies on UNIX pathnames may experience problems
on platform not using that. MSOS (MS Windows) used to use "\" instead of
"/". I hope that the old MacOS convention, which is used ":" is dead in the
new MacOS X.

But one simple way to avoid this is to remove the directory m4sugar: After
all, it contains only two files. Rename version.m4 to say sugar_version.m4
or something and alter the path in m4sugar.m4.

If there is a risk that people compile Bison under MSOS and you want to
avoid a lot of complaints in the mail lists, add config variable
DIRECTORY_SEPARATOR or something, for the slash/backslash.

If MSOS compilers have some kind of translation feature back and forth to
the UNIX path name convention, then there is no point in doing this, though.

  Hans Aberg