ctf: split the absolute-file-name caching machinery out of type_id()

We will be needing similar caching elsewhere in a forthcoming commit.

Signed-off-by: Nick Alcock <nick.alcock@oracle.com>

diff --git a/scripts/dwarf2ctf/dwarf2ctf.c b/scripts/dwarf2ctf/dwarf2ctf.c
index beca89222abf58532cff1c0dc2914436f6f490e2..224280dc10222c9aaf9209ed8983b01ed2f96a4a 100644 (file)
--- a/scripts/dwarf2ctf/dwarf2ctf.c
+++ b/scripts/dwarf2ctf/dwarf2ctf.c
@@ -608,6 +608,11 @@ static char *xstrdup(const char *s) __attribute__((__nonnull__,
  */
 static char *fn_to_module(const char *file_name);
 
+/*
+ * Determine, and cache, absolute filenames.
+ */
+static const char *abs_file_name(const char *file_name);
+
 /*
  * Stub libdwfl callback, use only the ELF handle passed in.
  */
@@ -1138,40 +1143,19 @@ static char *type_id(Dwarf_Die *die, void (*fun)(Dwarf_Die *die,
                        id = type_id(private_dwarf_type(die, &type_die), fun, data);
 
                /*
-                * Location information.  Here in particular we value speed over
-                * clarity, caching the result of realpath() to minimize system
-                * calls, and going to some length to keep the number of calls
-                * to str_append*() down.
+                * Location information.  We use cached realpath() results, and
+                * call str_appendn() only once, minimizing the number of
+                * strlen()s.
                 */
                if (id == NULL) {
-                       static GHashTable *abs_file_names;
-
-                       if (abs_file_names == NULL)
-                               abs_file_names = g_hash_table_new_full(g_str_hash,
-                                                                      g_str_equal,
-                                                                      free, free);
-
                        const char *decl_file_name = dwarf_decl_file(die);
                        int decl_line_num;
                        const char *fname = "";
-                       char line_num[21] = "";  /* bigger than 2^64's digit count */
+                       char line_num[21] = "";  /* bigger than 2^64's digit count */
 
                        no_type_id = 1;
                        if (decl_file_name != NULL) {
-
-                               fname = g_hash_table_lookup(abs_file_names,
-                                                           decl_file_name);
-
-                               if (fname == NULL) {
-                                       char abspath[PATH_MAX] = "";
-                                       if (realpath(decl_file_name, abspath) == NULL)
-                                               strcpy(abspath, decl_file_name);
-                                       g_hash_table_replace(abs_file_names,
-                                                            xstrdup(decl_file_name),
-                                                            xstrdup(abspath));
-                                       fname = g_hash_table_lookup(abs_file_names,
-                                                                   decl_file_name);
-                               }
+                               fname = abs_file_name(decl_file_name);
                        }
 
                        if (dwarf_decl_line(die, &decl_line_num) >= 0) {
@@ -3436,6 +3420,35 @@ static char *fn_to_module(const char *file_name)
        return module_name;
 }
 
+/*
+ * Determine, and cache, absolute filenames.  This is called in very hot
+ * paths, notably type_id(), and must be kept fast.
+ */
+static const char *abs_file_name(const char *file_name)
+{
+       static GHashTable *abs_file_names;
+       const char *abs_name;
+
+       if (abs_file_names == NULL)
+               abs_file_names = g_hash_table_new_full(g_str_hash, g_str_equal,
+                   free, free);
+
+       abs_name = g_hash_table_lookup(abs_file_names, file_name);
+
+       if (abs_name == NULL) {
+               char abspath[PATH_MAX] = "";
+
+               if (realpath(file_name, abspath) == NULL)
+                       strcpy(abspath, file_name);
+               g_hash_table_replace(abs_file_names,
+                   xstrdup(file_name), xstrdup(abspath));
+
+               abs_name = g_hash_table_lookup(abs_file_names, file_name);
+       }
+
+       return abs_name;
+}
+
 /*
  * Given a type encoding table, and a size, return the CTF encoding for that
  * type, or 0 if none.