Replace os_get_ltrace_conf_filename with os_get_ltrace_conf_filenames

- I.e. allow returning a list of filenames, as opposed to a single
  home directory name.  This is to implement exactly the legacy config
  file behavior on Linux.

Author: Petr Machata

backend.h

@@ -347,11 +347,16 @@ int arch_find_dl_debug(struct process *proc, arch_addr_t dyn_addr,
  * concern itself with it.  */
 int os_get_config_dirs(int private, const char ***retp);
 
-/* This is called to obtain the name of legacy config file, if any.
- * Returns 0 on success, in which case *RETP should be set to the file
- * name (it is legitimate to set this to NULL), or a negative value on
- * failure.  It is OK if the file is not present.  */
-int os_get_ltrace_conf_filename(const char **retp);
+/* This is called to obtain list of legacy config files to import, if
+ * any.  A reference to initialized vector of char* is passed in.
+ *
+ * This returns 0 on success, in which case strings from *RETP (if
+ * any) are interpreted as files names.  These files belong to the
+ * caller and will eventually be freed.
+ *
+ * Returns a negative value for failure, in which case *RETP contents
+ * are not consulted in any way.  */
+int os_get_ltrace_conf_filenames(struct vect *retp);
 
 /* If arch.h defines ARCH_HAVE_FETCH_ARG, the following callbacks have
  * to be implemented: arch_fetch_arg_init, arch_fetch_arg_clone,

configure.ac

@@ -226,6 +226,7 @@ LDFLAGS="${saved_LDFLAGS}"
 
 AM_CPPFLAGS=" \
 	-DSYSCONFDIR="'\"$(sysconfdir)\"'" \
+	-DPKGDATADIR="'\"$(pkgdatadir)\"'" \
 	${AM_CPPFLAGS} \
 	-I\$(top_srcdir)/sysdeps/${HOST_OS}/${HOST_CPU} \
 	-I\$(top_srcdir)/sysdeps/${HOST_OS} \

ltrace.1

@@ -291,10 +291,9 @@ instead.  For the main program binary, basename is considered as well
 
 When looking for a prototype library, ltrace potentially looks into
 several directories.  On Linux, those are $XDG_CONFIG_HOME/ltrace,
-$HOME/.ltrace, \fIX\fR/ltrace for each \fIX\fR in $XDG_CONFIG_DIRS,
-and /etc/ltrace (XXX but that should probably be /usr/lib/ltrace).  If
-the environment variable XDG_CONFIG_HOME is not defined, ltrace looks
-into $HOME/.config/ltrace instead.
+$HOME/.ltrace, \fIX\fR/ltrace for each \fIX\fR in $XDG_CONFIG_DIRS and
+/usr/share/ltrace.  If the environment variable XDG_CONFIG_HOME is not
+defined, ltrace looks into $HOME/.config/ltrace instead.
 
 There's also a mechanism for loading legacy config files.  If
 $HOME/.ltrace.conf exists it is imported to every loaded prototype

prototype.c

@@ -400,28 +400,38 @@ load_config(struct protolib_cache *cache,
 	return 0;
 }
 
+static enum callback_status
+import_legacy_file(char **fnp, void *data)
+{
+	struct protolib_cache *cache = data;
+	struct protolib *plib = protolib_cache_file(cache, *fnp, 1);
+	if (plib != NULL) {
+		/* The cache now owns the file name.  */
+		*fnp = NULL;
+		if (protolib_add_import(&cache->imports, plib) < 0)
+			return CBS_STOP;
+	}
+
+	return CBS_CONT;
+}
+
 static int
 add_ltrace_conf(struct protolib_cache *cache)
 {
 	/* Look into private config directories for .ltrace.conf and
 	 * into system config directories for ltrace.conf.  If it's
 	 * found, add it to implicit import module.  */
-	struct protolib *plib = NULL;
-	const char *home = NULL;
-	if (os_get_ltrace_conf_filename(&home) < 0
-	    || (home != NULL
-		&& (plib = consider_config_dir(cache, home, ".ltrace")) != NULL
-		&& protolib_add_import(&cache->imports, plib) < 0)
-	    || (plib == NULL && load_config(cache, "ltrace", 0, &plib) < 0)
-	    || (plib != NULL && protolib_add_import(&cache->imports, plib) < 0))
-		/* N.B. If plib is non-NULL, it has been already
-		 * cached.  We don't therefore destroy it on
-		 * failures.  */
+	struct vect legacy_files;
+	VECT_INIT(&legacy_files, char *);
+	if (os_get_ltrace_conf_filenames(&legacy_files) < 0) {
+		vect_destroy(&legacy_files, NULL, NULL);
 		return -1;
+	}
 
-	/* Never mind whether we've found anything.  It's fine if the
-	 * config is absent.  */
-	return 0;
+	int ret = VECT_EACH(&legacy_files, char *, NULL,
+			    import_legacy_file, cache) == NULL ? 0 : -1;
+	VECT_DESTROY(&legacy_files, char *, vect_dtor_string, NULL);
+	return ret;
 }
 
 static enum callback_status

sysdeps/linux-gnu/hooks.c

@@ -161,10 +161,10 @@ os_get_config_dirs(int private, const char ***retp)
 		VECT_DESTROY(&v, struct opt_F_t, destroy_opt_F_cb, NULL);
 	}
 
-	/* SYSCONFDIR is passed via -D when compiling.  */
-	const char *sysconfdir = SYSCONFDIR;
-	if (sysconfdir != NULL)
-		add_dir(&dirs, sysconfdir, "");
+	/* PKGDATADIR is passed via -D when compiling.  */
+	const char *pkgdatadir = PKGDATADIR;
+	if (pkgdatadir != NULL)
+		add_dir(&dirs, pkgdatadir, "");
 
 	if (VECT_PUSHBACK(&dirs, &delim) < 0)
 		goto fail;
@@ -173,10 +173,39 @@ os_get_config_dirs(int private, const char ***retp)
 }
 
 int
-os_get_ltrace_conf_filename(const char **retp)
+os_get_ltrace_conf_filenames(struct vect *retp)
 {
+	char *homepath = NULL;
+	char *syspath = NULL;
+
+#define FN ".ltrace.conf"
 	if (g_home_dir == NULL)
 		os_get_config_dirs(0, NULL);
-	*retp = g_home_dir;
-	return g_home_dir != NULL ? 0 : -1;
+
+	if (g_home_dir != NULL) {
+		homepath = malloc(strlen(g_home_dir) + 1 + sizeof FN);
+		if (homepath == NULL
+		    || sprintf(homepath, "%s/%s", g_home_dir, FN) < 0) {
+		fail:
+			free(syspath);
+			free(homepath);
+			return -1;
+		}
+	}
+
+	/* SYSCONFDIR is passed via -D when compiling.  */
+	const char *sysconfdir = SYSCONFDIR;
+	if (sysconfdir != NULL && *sysconfdir != '\0') {
+		/* No +1, we skip the initial period.  */
+		syspath = malloc(strlen(sysconfdir) + sizeof FN);
+		if (syspath == NULL
+		    || sprintf(syspath, "%s/%s", sysconfdir, FN + 1) < 0)
+			goto fail;
+	}
+
+	if (VECT_PUSHBACK(retp, &homepath) < 0
+	    || VECT_PUSHBACK(retp, &syspath) < 0)
+		goto fail;
+
+	return 0;
 }

vect.c

@@ -202,3 +202,9 @@ vect_each_cst(const struct vect *vec, const void *start_after,
 	return vect_each((struct vect *)vec, (void *)start_after,
 			 (void *)cb, data);
 }
+
+void
+vect_dtor_string(char **key, void *data)
+{
+	free(*key);
+}

vect.h

@@ -204,4 +204,8 @@ void vect_qsort(struct vect *vec, int (*compar)(const void *, const void *));
 			   (int (*)(const void *, const void *))_compar); \
 	} while (0)
 
+
+/* A dtor which calls 'free' on elements of a vector.  */
+void vect_dtor_string(char **key, void *data);
+
 #endif /* VECT_H */