Bug#551017: imagemagick: FTBFS on hurd-i386: wrong PATH_MAX and /proc usage

[Pino Toscano]

Package: imagemagick
Version: 7:6.5.5.3-1
Severity: important
Tags: patch
User: debian-h...@lists.debian.org
Usertags: hurd

Hi,

as shown in [1], currently imagemagick does not build on GNU/Hurd.
The reason is in magick/utility.c, in the implementation of GetExecutionPath():
Hurd has both getpid() and readlink(), so the
  #if defined(MAGICKCORE_HAVE_GETPID) && defined(MAGICKCORE_HAVE_READLINK)
  [...]
  #endif
code block is used. Although, this block has two problems for Hurd:
- inconditional usage of PATH_MAX (which is not a problem, as it could be fixed)
- use of /proc/$PID/{exe,file}; Hurd's proc have none of those two, so the code
  there would be unuseful anyway

The solution I chose was to exclude that block for Hurd, and add a new
Hurd-specific block which makes use of the GNU-specific program_invocation_name
extern variable (see /usr/include/errno.h) - and cwd if program_invocation_name
is relative - to get the absolute path of the execution application.

[1] 
http://buildd.debian-ports.org/fetch.php?&pkg=imagemagick&ver=7:6.5.5.3-1&arch=hurd-i386&stamp=1251687730&file=log&as=raw

Thanks,
-- 
Pino

--- imagemagick-6.5.5.3.orig/magick/utility.c
+++ imagemagick-6.5.5.3/magick/utility.c
@@ -904,7 +904,7 @@
 
   *path='\0';
   cwd=getcwd(path,(unsigned long) extent);
-#if defined(MAGICKCORE_HAVE_GETPID) && defined(MAGICKCORE_HAVE_READLINK)
+#if defined(MAGICKCORE_HAVE_GETPID) && defined(MAGICKCORE_HAVE_READLINK) && !defined(__GNU__)
   {
     char
       link_path[MaxTextExtent],
@@ -961,6 +961,46 @@
 #if defined(__WINDOWS__)
   NTGetExecutionPath(path,extent);
 #endif
+#if defined(__GNU__)
+  {
+    char
+      *buffer,
+      *exec_path;
+
+    MagickBooleanType
+      free_buffer;
+
+    size_t
+      buffer_length;
+
+    long
+      count;
+
+    free_buffer = MagickFalse;
+    count = 0;
+    exec_path = NULL;
+    if (program_invocation_name[0] == '/')
+      {
+        buffer = program_invocation_name;
+      }
+    else
+      {
+        buffer_length = strlen(cwd) + 1 + strlen(program_invocation_name) + 1;
+        buffer = malloc(buffer_length);
+        free_buffer = MagickTrue;
+        count = FormatMagickString(buffer,buffer_length,"%s/%s",cwd,program_invocation_name);
+      }
+    if (count != -1)
+      {
+        exec_path = realpath(buffer,NULL);
+        if (exec_path)
+          CopyMagickString(path,exec_path,extent);
+      }
+    if (free_buffer)
+      free(buffer);
+    free(exec_path);
+  }
+#endif
   return(IsPathAccessible(path));
 }