logger: make "global_config" truly global

Finish the job that commit 5b29dae9c8 ("logger: Create global
convert_config variable to avoid spaghetti code.") started but did not
finish, leaving behind a supposedly "global" variable that is actually a
confusing global pointer to a struct local to the main() function.

This confuses some static analyzer complaining that stack values are
being returned, see #6858 and #6738. This is a false positive
because the main()'s stack lifespan is the same as a global but let's
simplify things anyway.

Also stop using 'extern' in .c files, use a proper .h file instead.

Signed-off-by: Marc Herbert <marc.herbert@intel.com>

tools/logger/convert.c

@@ -65,9 +65,6 @@ static const char *BAD_PTR_STR = "<bad uid ptr 0x%.8x>";
 #define UUID_LOWER "%s%s%s<%08x-%04x-%04x-%02x%02x-%02x%02x%02x%02x%02x%02x>%s%s%s"
 #define UUID_UPPER "%s%s%s<%08X-%04X-%04X-%02X%02X-%02X%02X%02X%02X%02X%02X>%s%s%s"
 
-/* pointer to config for global context */
-struct convert_config *global_config;
-
 static int read_entry_from_ldc_file(struct ldc_entry *entry, uint32_t log_entry_address);
 
 char *format_uid_raw(const struct sof_uuid_entry *uid_entry, int use_colors, int name_first,
@@ -1037,14 +1034,20 @@ static int dump_ldc_info(void)
 	return 0;
 }
 
-int convert(struct convert_config *config)
+int convert(void)
 {
 	struct snd_sof_logs_header snd;
 	struct snd_sof_uids_header uids_hdr;
 	int count, ret = 0;
 
+	/* const pointer initialized at build time */
+	if (!global_config)
+		abort();
+
+	/* just a shorter alias */
+	struct convert_config * const config = global_config;
+
 	config->logs_header = &snd;
-	global_config = config;
 
 	count = fread(&snd, sizeof(snd), 1, config->ldc_fd);
 	if (!count) {

tools/logger/convert.h

@@ -47,4 +47,8 @@ struct convert_config {
 };
 
 uint32_t get_uuid_key(const struct sof_uuid_entry *entry);
-int convert(struct convert_config *config);
+
+/* pointer to config for global context */
+extern struct convert_config * const global_config;
+
+int convert(void);

tools/logger/filter.c

@@ -22,8 +22,6 @@
 #define COMPONENTS_SEPARATOR ','
 #define COMPONENT_NAME_SCAN_STRING_LENGTH 32
 
-extern struct convert_config *global_config;
-
 /** map between log level given by user and enum value */
 static const struct {
 	const char name[16];

tools/logger/logger.c

@@ -282,6 +282,8 @@ cleanup:
 }
 #endif // HAS_INOTIFY
 
+static struct convert_config _global_config;
+struct convert_config * const global_config = &_global_config;
 
 int main(int argc, char *argv[])
 {
@@ -498,7 +500,8 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	ret = -convert(&config);
+	_global_config = config;
+	ret = -convert();
 
 out:
 	/* free memory */

tools/logger/misc.c

@@ -41,8 +41,6 @@ char *log_asprintf(const char *format, ...)
 	return result;
 }
 
-extern struct convert_config *global_config;
-
 /** Prints 1. once to stderr. 2. a second time to the global out_fd if
  * out_fd is neither stderr nor stdout (because the -o option was used).
  */