[tex-k] ~ expansion in TEXMFLOCAL from Knuth

[Olaf Weber]

Thomas Esser writes:

> Hi,
> I have found the bug. Interestingly, if one compares TEXMFLOCAL / TEXMFHOME, there
> is a difference:

>   $ TEXMFHOME='~/sunburn/texmf' kpsewhich cmrfunny.tfm
>   /home/te/sunburn/texmf/fonts/tfm/foo/baa/cmrfunny.tfm

>   $ TEXMFLOCAL='~/sunburn/texmf' kpsewhich cmrfunny.tfm

> The difference is the use of the !! prefix in the TEXMF definition:
>   TEXMF = {...,$TEXMFHOME,...,!!$TEXMFLOCAL,...}

> Finally, I have found that kpse_tilde_expand() in tilde.c does not expand
> a tilde in an element such as
>   !!~/sunburn/texmf/fonts/tfm//
> because of

>   /* If no leading tilde, do nothing.  */
>   if (*name != '~') {

> So, this code has to be rewritten to take care of the !! prefix.

I've got a diff based on, but not identical to, code that Thomas sent
me directly:

$ cvs diff -u -rtexk-7_5_4 tilde.c
Index: tilde.c
===================================================================
RCS file: /usr/local/cvsroot/texk/texk/kpathsea/tilde.c,v
retrieving revision 1.3
retrieving revision 1.5
diff -u -r1.3 -r1.5
--- tilde.c     4 May 1998 17:47:33 -0000       1.3
+++ tilde.c     10 Apr 2005 19:55:30 -0000      1.5
@@ -1,5 +1,6 @@
 /* tilde.c: Expand user's home directories.

+Copyright (C) 2005, Olaf Weber.
 Copyright (C) 1993, 95, 96, 97 Karl Berry.

 This library is free software; you can redistribute it and/or
@@ -35,11 +36,25 @@
 {
   const_string expansion;
   const_string home;
+  const_string prefix;

   assert (name);
+
+  /* If there is a leading "!!", set prefix to "!!", otherwise use
+     the empty string.  After this, we can test whether a prefix was
+     found by checking *prefix, and it is safe to unconditionally
+     prepend it. */
+  if (name[0] == '!' && name[1] == '!') {
+    name += 2;
+    prefix = "!!";
+  } else {
+    prefix = "";
+  }

-  /* If no leading tilde, do nothing.  */
+  /* If no leading tilde, do nothing, and return the original string.  */
   if (*name != '~') {
+    if (*prefix)
+      name -= 2;
     expansion = name;

   /* If a bare tilde, return the home directory or `.'.  (Very unlikely
@@ -49,7 +64,7 @@
     if (!home) {
       home = ".";
     }
-    expansion = xstrdup (home);
+    expansion = concat (prefix, home);

   /* If `~/', remove any trailing / or replace leading // in $HOME.
      Should really check for doubled intermediate slashes, too.  */
@@ -65,13 +80,12 @@
     if (IS_DIR_SEP (home[strlen (home) - 1])) {        /* omit / after ~ */
       c++;
     }
-    expansion = concat (home, name + c);
+    expansion = concat3 (prefix, home, name + c);

   /* If `~user' or `~user/', look up user in the passwd database (but
      OS/2 doesn't have this concept.  */
-  } else
+  } else {
 #ifdef HAVE_PWD_H
-    {
       struct passwd *p;
       string user;
       unsigned c = 2;
@@ -95,12 +109,15 @@
       if (IS_DIR_SEP (home[strlen (home) - 1]) && name[c] != 0)
         c++; /* If HOME ends in /, omit the / after ~user. */

-      expansion = name[c] == 0 ? xstrdup (home) : concat (home, name + c);
-    }
+      expansion = concat3 (prefix, home, name + c);
 #else /* not HAVE_PWD_H */
-    expansion = name;
+      /* Since we don't know how to look up a user name, just return the
+         original string. */
+      if (*prefix)
+        name -= 2;
+      expansion = name;
 #endif /* not HAVE_PWD_H */
-
+  }
   /* We may return the same thing as the original, and then we might not
      be returning a malloc-ed string.  Callers beware.  Sorry.  */
   return (string) expansion;
@@ -128,6 +145,12 @@
   test_expand_tilde ("~root");
   test_expand_tilde ("~");
   test_expand_tilde ("foo~bar");
+
+  test_expand_tilde ("!!");
+  test_expand_tilde ("!!none");
+  test_expand_tilde ("!!~root");
+  test_expand_tilde ("!!~");
+  test_expand_tilde ("!!foo~bar");

   return 0;
 }

-- 
Olaf Weber

               (This space left blank for technical reasons.)