osxlaunch: add diagnostics under an #ifdef.

Now I can compile with -DDEBUG_OSXLAUNCH and see exactly what the
program is doing, if I suspect it of misbehaviour.

unix/osxlaunch.c

@@ -352,19 +352,35 @@ char *alloc_cat(const char *str1, const char *str2)
  * Overwrite an environment variable, preserving the old one for the
  * real app to restore.
  */
+void setenv_wrap(const char *name, const char *value)
+{
+#ifdef DEBUG_OSXLAUNCH
+    printf("setenv(\"%s\",\"%s\")\n", name, value);
+#endif
+    setenv(name, value, 1);
+}
+
+void unsetenv_wrap(const char *name)
+{
+#ifdef DEBUG_OSXLAUNCH
+    printf("unsetenv(\"%s\")\n", name);
+#endif
+    unsetenv(name);
+}
+
 char *prefix, *prefixset, *prefixunset;
 void overwrite_env(const char *name, const char *value)
 {
     const char *oldvalue = getenv(name);
     if (oldvalue) {
-        setenv(alloc_cat(prefixset, name), oldvalue, 1);
+        setenv_wrap(alloc_cat(prefixset, name), oldvalue);
     } else {
-        setenv(alloc_cat(prefixunset, name), "", 1);
+        setenv_wrap(alloc_cat(prefixunset, name), "");
     }
     if (value)
-        setenv(name, value, 1);
+        setenv_wrap(name, value);
     else
-        unsetenv(name);
+        unsetenv_wrap(name);
 }
 
 /* ----------------------------------------------------------------------
@@ -377,6 +393,11 @@ int main(int argc, char **argv)
     prefixset = alloc_cat(prefix, "s");
     prefixunset = alloc_cat(prefix, "u");
 
+#ifdef DEBUG_OSXLAUNCH
+    printf("Environment prefixes: main=\"%s\", set=\"%s\", unset=\"%s\"\n",
+           prefix, prefixset, prefixunset);
+#endif
+
     char *prog_path = get_program_path(); // <bundle>/Contents/MacOS/<filename>
     char *macos = dirname_wrapper(prog_path); // <bundle>/Contents/MacOS
     char *contents = dirname_wrapper(macos);  // <bundle>/Contents
@@ -412,17 +433,30 @@ int main(int argc, char **argv)
     }
     int j = 0;
     new_argv[j++] = realbin;
+#ifdef DEBUG_OSXLAUNCH
+    printf("argv[%d] = \"%s\"\n", j-1, new_argv[j-1]);
+#endif
     {
         int i = 1;
         if (i < argc && !strncmp(argv[i], "-psn_", 5))
             i++;
 
-        for (; i < argc; i++)
+        for (; i < argc; i++) {
             new_argv[j++] = argv[i];
+#ifdef DEBUG_OSXLAUNCH
+            printf("argv[%d] = \"%s\"\n", j-1, new_argv[j-1]);
+#endif
+        }
     }
     new_argv[j++] = prefix;
+#ifdef DEBUG_OSXLAUNCH
+    printf("argv[%d] = \"%s\"\n", j-1, new_argv[j-1]);
+#endif
     new_argv[j++] = NULL;
 
+#ifdef DEBUG_OSXLAUNCH
+    printf("executing \"%s\"\n", realbin);
+#endif
     execv(realbin, new_argv);
     perror("execv");
     free(new_argv);