xdo_search: fix improper memfrees, pre-compile regexes optimization

[Cycatz]

The patch was originally from @Lekensteyn at this commit in #36, I merged it with HEAD and also made some changes.

The commit fixes #258, which is causing by freeing uninitialized regex_t objects due to short-circuit evaluation.

if (!compile_re(search->title, &title_re) \
    || !compile_re(search->winclass, &class_re) \
    || !compile_re(search->winclassname, &classname_re) \
    || !compile_re(search->winrole, &role_re) \
    || !compile_re(search->winname, &name_re)) {

  regfree(&title_re);
  regfree(&class_re);
  regfree(&classname_re);
  regfree(&name_re);
  regfree(&role_re);

  return False;
}

The regex pre-compiled solution initializes the content of these regex_t objects to zero using memset so that regfrees don't crash.

In addition, the origin patch also resolves the issue of repeated error messages by compiling regex_t objects at start. These are all done by @Lekensteyn, awesome!

Aside from resolving merging conflicts, I add regex_t struct for role, rename xdg_search_re to xdg_regex_t for style consistency and apply the changes that constantify regex_t* where applicable from @Lekensteyn.

BTW, I remove the whitespaces removal code changes, I think it should be made in other commit. If there is any need, I can help with that.

[aldot]

This is one of those cases where one would usually use a goto, but given we don't have a single goto in there ATM, i doubt this would be well received.

I think i would prefer the much simpler tweak, although it could rightfully be considered looking ugly and annoyingly repetitive:

diff --git a/xdo_search.c b/xdo_search.c
index 9842927..258a9d7 100644
--- a/xdo_search.c
+++ b/xdo_search.c
@@ -210,11 +210,10 @@ static int _xdo_match_window_pid(const xdo_t *xdo, Window window, const int pid)
 static int compile_re(const char *pattern, regex_t *re) {
   int ret;
   if (pattern == NULL) {
-    regcomp(re, "^$", REG_EXTENDED | REG_ICASE);
-    return True;
+    ret = regcomp(re, "^$", REG_EXTENDED | REG_ICASE);
+  } else {
+    ret = regcomp(re, pattern, REG_EXTENDED | REG_ICASE);
   }
-
-  ret = regcomp(re, pattern, REG_EXTENDED | REG_ICASE);
   if (ret != 0) {
     fprintf(stderr, "Failed to compile regex (return code %d): '%s'\n", ret, pattern);
     return False;
@@ -240,12 +239,28 @@ static int check_window_match(const xdo_t *xdo, Window wid,
   regex_t role_re;
 
 
-  if (!compile_re(search->title, &title_re) \
-      || !compile_re(search->winclass, &class_re) \
-      || !compile_re(search->winclassname, &classname_re) \
-      || !compile_re(search->winrole, &role_re) \
-      || !compile_re(search->winname, &name_re)) {
+  if (!compile_re(search->title, &title_re)) {
+    return False;
+  }
+  if (!compile_re(search->winclass, &class_re)) {
+    regfree(&title_re);
 
+    return False;
+  }
+  if (!compile_re(search->winclassname, &classname_re)) {
+    regfree(&title_re);
+    regfree(&class_re);
+
+    return False;
+  }
+  if (!compile_re(search->winrole, &role_re)) {
+    regfree(&title_re);
+    regfree(&class_re);
+    regfree(&classname_re);
+
+    return False;
+  }
+  if (!compile_re(search->winname, &name_re)) {
     regfree(&title_re);
     regfree(&class_re);
     regfree(&classname_re);

Just a thought.
PS: beware, i didn't even try to compile the hunk above, this is for illustrative purpose only!
PPS: the compile_re hunk should be committed separately, "Check regcomp even for NULL pattern" or the like. Not strictly needed but it looks odd NOT to check if "^$" compiled. Unlikely, but just for good measure.
HTH,