+/*----------------------.
+| Run our backend, M4. |
+`----------------------*/
+
+static void
+m4_invoke (const char *definitions)
+{
+ /* Invoke m4 on the definition of the muscles, and the skeleton. */
+ const char *bison_pkgdatadir = getenv ("BISON_PKGDATADIR");
+ const char *m4 = getenv ("M4");
+ int pkg_data_len;
+ char *full_skeleton;
+
+ if (!m4)
+ m4 = M4;
+ if (!bison_pkgdatadir)
+ bison_pkgdatadir = PKGDATADIR;
+ pkg_data_len = strlen (bison_pkgdatadir);
+ full_skeleton = XMALLOC (char, pkg_data_len + strlen (skeleton) + 2);
+ if (bison_pkgdatadir[pkg_data_len-1] == '/')
+ sprintf (full_skeleton, "%s%s", bison_pkgdatadir, skeleton);
+ else
+ sprintf (full_skeleton, "%s/%s", bison_pkgdatadir, skeleton);
+ if (trace_flag)
+ fprintf (stderr,
+ "running: %s -I %s m4sugar/m4sugar.m4 %s %s\n",
+ m4, bison_pkgdatadir, definitions, full_skeleton);
+ skel_in = readpipe (m4,
+ "-I", bison_pkgdatadir,
+ "m4sugar/m4sugar.m4",
+ definitions,
+ full_skeleton,
+ NULL);
+ XFREE (full_skeleton);
+ if (!skel_in)
+ error (EXIT_FAILURE, errno, "cannot run m4");
+ skel_lex ();
+
+}
+