Account for different implementations of realpath(3)

src/odt.c

@@ -72,9 +72,40 @@ createOutputDocument(const char* const outputFilename, const char* const tempDir
     pid_t child_pid;
     if ((child_pid = fork()) == 0) {
         /* you are the child */
+
+	/* In some implementations, realpath will give an error
+	 * if the file does not exist, so we need to run it on
+	 * the output directory, not the as-yet nonexistent
+	 * output filename. That's what all this (below) is for. */
+	char outputDir[FILENAME_MAX];
+	char outputBase[FILENAME_MAX];
         char outputRealPath[FILENAME_MAX];
+	strncpy(outputDir, outputFilename, FILENAME_MAX);
+	char *ptr = strrchr(outputDir, '/');
+	if (ptr) {
+	    strncpy(outputBase, ptr + 1, FILENAME_MAX);
+	    *(ptr + 1) = '\0';
+	} else {
+	    strncpy(outputDir, ".", FILENAME_MAX);
+	    strncpy(outputBase, outputFilename, FILENAME_MAX);
+	}
+
+        if (realpath(outputDir, outputRealPath) == NULL) {
+            /* hopefully this doesn't run, but it will give good info
+	     * if it does */
+	    perror("realpath");
+	    fprintf(stderr, "outputFilename was \"%s\"\n", outputFilename);
+	    char curdir[FILENAME_MAX];
+	    getcwd(curdir, FILENAME_MAX);
+	    fprintf(stderr, "curdir was \"%s\"\n", curdir);
+	    exit(1);
+	}
+
+	/* Then we append the output filename. */
+	strncat(outputRealPath, "/", FILENAME_MAX);
+	strncat(outputRealPath, outputBase, FILENAME_MAX);
+
         char* const args[] = { "zip", "-r", outputRealPath, "mimetype", ".", NULL };
-        realpath(outputFilename, outputRealPath);
         chdir(tempDir);
         freopen("/dev/null", "w", stdout);
         execvp("zip", args);