print out all malloc_conf settings in stats

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -38,6 +38,9 @@ extern atomic_zu_t zero_realloc_count;
 extern bool opt_cache_oblivious;
 extern unsigned opt_debug_double_free_max_scan;
 
+extern char malloc_conf_file[PATH_MAX + 1];
+extern char malloc_conf_env_var[PATH_MAX + 1];
+
 /* Escape free-fastpath when ptr & mask == 0 (for sanitization purpose). */
 extern uintptr_t san_cache_bin_nonfast_mask;
 

src/ctl.c

@@ -80,6 +80,10 @@ CTL_PROTO(thread_allocatedp)
 CTL_PROTO(thread_deallocated)
 CTL_PROTO(thread_deallocatedp)
 CTL_PROTO(thread_idle)
+CTL_PROTO(malloc_conf_global_var_malloc_conf)
+CTL_PROTO(malloc_conf_file)
+CTL_PROTO(malloc_conf_env_var)
+CTL_PROTO(malloc_conf_global_var_malloc_conf_2_conf_harder)
 CTL_PROTO(config_cache_oblivious)
 CTL_PROTO(config_debug)
 CTL_PROTO(config_fill)
@@ -920,6 +924,15 @@ static const ctl_named_node_t experimental_node[] = {
 	{NAME("thread"),	CHILD(named, experimental_thread)}
 };
 
+static const ctl_named_node_t malloc_conf_node[] = {
+	{NAME("global_var_malloc_conf"),
+	    CTL(malloc_conf_global_var_malloc_conf)},
+	{NAME("file"),			CTL(malloc_conf_file)},
+	{NAME("env_var"),		CTL(malloc_conf_env_var)},
+	{NAME("global_var_malloc_conf_2_conf_harder"),
+	    CTL(malloc_conf_global_var_malloc_conf_2_conf_harder)}
+};
+
 static const ctl_named_node_t	root_node[] = {
 	{NAME("version"),	CTL(version)},
 	{NAME("epoch"),		CTL(epoch)},
@@ -933,7 +946,8 @@ static const ctl_named_node_t	root_node[] = {
 	{NAME("arenas"),	CHILD(named, arenas)},
 	{NAME("prof"),		CHILD(named, prof)},
 	{NAME("stats"),		CHILD(named, stats)},
-	{NAME("experimental"),	CHILD(named, experimental)}
+	{NAME("experimental"),	CHILD(named, experimental)},
+	{NAME("malloc_conf"),	CHILD(named, malloc_conf)}
 };
 static const ctl_named_node_t super_root_node[] = {
 	{NAME(""),		CHILD(named, root)}
@@ -1986,6 +2000,16 @@ label_return:								\
 
 CTL_RO_NL_GEN(version, JEMALLOC_VERSION, const char *)
 
+CTL_RO_NL_CGEN(je_malloc_conf, malloc_conf_global_var_malloc_conf,
+    je_malloc_conf, const char *)
+CTL_RO_NL_CGEN(malloc_conf_file, malloc_conf_file, malloc_conf_file,
+    const char *)
+CTL_RO_NL_CGEN(malloc_conf_env_var, malloc_conf_env_var,
+    malloc_conf_env_var, const char *)
+CTL_RO_NL_CGEN(je_malloc_conf_2_conf_harder,
+    malloc_conf_global_var_malloc_conf_2_conf_harder,
+    je_malloc_conf_2_conf_harder, const char *)
+
 static int
 epoch_ctl(tsd_t *tsd, const size_t *mib, size_t miblen,
     void *oldp, size_t *oldlenp, void *newp, size_t newlen) {

src/jemalloc.c

@@ -57,6 +57,9 @@ const char	*je_malloc_conf_2_conf_harder
 #endif
     ;
 
+char malloc_conf_file[PATH_MAX + 1];
+char malloc_conf_env_var[PATH_MAX + 1];
+
 bool	opt_abort =
 #ifdef JEMALLOC_DEBUG
     true
@@ -1009,6 +1012,8 @@ obtain_malloc_conf(unsigned which_source, char buf[PATH_MAX + 1]) {
 			set_errno(saved_errno);
 		}
 #endif
+		strncpy(malloc_conf_file, buf, linklen);
+		malloc_conf_file[linklen] = '\0';
 		buf[linklen] = '\0';
 		ret = buf;
 		break;
@@ -1026,6 +1031,8 @@ obtain_malloc_conf(unsigned which_source, char buf[PATH_MAX + 1]) {
 			 * Do nothing; opts is already initialized to the value
 			 * of the MALLOC_CONF environment variable.
 			 */
+			strncpy(malloc_conf_env_var, ret, PATH_MAX);
+			malloc_conf_env_var[PATH_MAX] = '\0';
 		} else {
 			/* No configuration specified. */
 			ret = NULL;

src/stats.c

@@ -1430,6 +1430,43 @@ stats_general_print(emitter_t *emitter) {
 #undef CONFIG_WRITE_BOOL
 	emitter_dict_end(emitter); /* Close "config" dict. */
 
+	/*
+	 * malloc_conf.
+	 *
+	 * Sources are documented in https://jemalloc.net/jemalloc.3.html#tuning
+	 * - (Not Included Here) The string specified via --with-malloc-conf,
+	 *     which is already printed out above as config.malloc_conf
+	 * - (Included) The string pointed to by the global variable malloc_conf
+	 * - (Included) The “name” of the file referenced by the symbolic link
+	 *     named /etc/malloc.conf
+	 * - (Included) The value of the environment variable MALLOC_CONF
+	 * - (Optional, Internal) The string pointed to by the global variable
+	 *     malloc_conf_2_conf_harder, which is hidden from the public.
+	 *
+	 * Note: The outputs are strictly ordered by priorities (low -> high).
+	 *
+	 * */
+#define MALLOC_CONF_WRITE(name, message)					\
+	if (je_mallctl("malloc_conf."name, (void *)&cpv, &cpsz, NULL, 0) !=	\
+	    0) {								\
+		cpv = "";							\
+	}									\
+	emitter_kv(emitter, name, message, emitter_type_string,	&cpv);
+
+	emitter_dict_begin(emitter, "malloc_conf", "Tuning settings");
+	MALLOC_CONF_WRITE("global_var_malloc_conf", "Global variable malloc_conf");
+	MALLOC_CONF_WRITE("file", "Symbolic link malloc.conf");
+	MALLOC_CONF_WRITE("env_var", "Environment variable MALLOC_CONF");
+	/* As this config is internal only, skip the output if it's NULL */
+	if (je_mallctl("malloc_conf.global_var_malloc_conf_2_conf_harder",
+	    (void *)&cpv, &cpsz, NULL, 0) == 0) {
+		emitter_kv(emitter, "global_var_malloc_conf_2_conf_harder", "Global "
+		    "variable malloc_conf_2_conf_harder", emitter_type_string, &cpv);
+	}
+	emitter_dict_end(emitter); /* Close "malloc_conf" dict. */
+
+#undef MALLOC_CONF_WRITE
+
 	/* opt. */
 #define OPT_WRITE(name, var, size, emitter_type)			\
 	if (je_mallctl("opt."name, (void *)&var, &size, NULL, 0) ==	\

test/unit/malloc_conf_2.c

@@ -22,8 +22,31 @@ TEST_BEGIN(test_malloc_conf_2) {
 }
 TEST_END
 
+TEST_BEGIN(test_mallctl_global_var) {
+#ifdef _WIN32
+	bool windows = true;
+#else
+	bool windows = false;
+#endif
+	/* Windows doesn't support weak symbol linker trickery. */
+	test_skip_if(windows);
+
+	const char *mc;
+	size_t sz = sizeof(mc);
+	expect_d_eq(mallctl("malloc_conf.global_var_malloc_conf",
+	    (void *)&mc, &sz, NULL, 0), 0, "Unexpected mallctl() failure");
+	expect_str_eq(mc, malloc_conf, "Unexpected value for malloc_conf");
+
+	expect_d_eq(mallctl("malloc_conf.global_var_malloc_conf_2_conf_harder",
+	    (void *)&mc, &sz, NULL, 0), 0, "Unexpected mallctl() failure");
+	expect_str_eq(mc, malloc_conf_2_conf_harder, "Unexpected value for "
+	    "malloc_conf_2_conf_harder");
+}
+TEST_END
+
 int
 main(void) {
 	return test(
-	    test_malloc_conf_2);
+	    test_malloc_conf_2,
+	    test_mallctl_global_var);
 }