[metapost] using MPXMAINCMD fails when it contains space

Martin Budaj m.budaj at gmail.com
Thu May 21 18:53:51 CEST 2009

Hi all,

there is a problem when trying to use metapost btex...etex labels in
the Windows environment where 1) tex binary is not in a path and 2)
its installation directory contains space.

Older metapost version (0.641) had no problems using
in texmf.cnf to generate labels. For latest version (1.200) I changed it to
but metapost fails (producing no mpxerr.log as advised)

  fatal: Command failed: "C:/Program Files/Therion/bin/win32/tex.exe"
--parse-first-line --interaction=nonstopmode mpa02804.tex; see

The old way of running external makempx binary doesn't work either,
giving the message

  makempx: Command failed: mpto -tex ./data.mp

After some experiments it seems that the function spawnvp(P_WAIT, cmd,
options) requires that cmd MUST NOT be enclosed in quotes but
options[0] MUST be enclosed in quotes if the path contains a space.
After deleting the quotation marks in cmd (patch attached below) the
label generation works fine using the new method (without external

I am not sure if all windows version require this modification (tested
just on XP).

Best regards,

--- mpxout.w.old        2009-05-21 18:41:39 +0200
+++ mpxout.w    2009-05-21 18:00:54 +0200
@@ -3952,7 +3952,15 @@
    return retcode;
-   return spawnvp(P_WAIT, cmd, (const char **)options);
+   char * tmps = xmalloc(strlen(cmd)+1,1);
+   if (cmd[0] != '"') strcpy(tmps,cmd);
+   else {
+     strncpy(tmps,cmd+1,strlen(cmd)-2);
+     tmps[strlen(cmd)-2] = 0;
+   }
+   return spawnvp(P_WAIT, tmps, (const char **)options);

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