Make eligible global variables static and/or const

For better or worse, Jemalloc has a significant number of global
variables. Making all eligible global variables `static` and/or `const`
at least makes it slightly easier to reason about them, as these
qualifications communicate to the programmer restrictions on their use
without having to `grep` the whole codebase.

include/jemalloc/internal/arena_externs.h

@@ -18,11 +18,10 @@ extern ssize_t opt_dirty_decay_ms;
 extern ssize_t opt_muzzy_decay_ms;
 
 extern percpu_arena_mode_t opt_percpu_arena;
-extern const char *percpu_arena_mode_names[];
+extern const char *const percpu_arena_mode_names[];
 
 extern div_info_t arena_binind_div_info[SC_NBINS];
 
-extern malloc_mutex_t arenas_lock;
 extern emap_t arena_emap_global;
 
 extern size_t opt_oversize_threshold;

include/jemalloc/internal/base.h

@@ -23,7 +23,7 @@ typedef enum metadata_thp_mode_e metadata_thp_mode_t;
 
 #define METADATA_THP_DEFAULT metadata_thp_disabled
 extern metadata_thp_mode_t opt_metadata_thp;
-extern const char *metadata_thp_mode_names[];
+extern const char *const metadata_thp_mode_names[];
 
 
 /* Embedded at the beginning of every block of base-managed virtual memory. */

include/jemalloc/internal/extent_dss.h

@@ -11,7 +11,7 @@ typedef enum {
 #define DSS_PREC_DEFAULT dss_prec_secondary
 #define DSS_DEFAULT "secondary"
 
-extern const char *dss_prec_names[];
+extern const char *const dss_prec_names[];
 
 extern const char *opt_dss;
 

include/jemalloc/internal/hpa_hooks.h

@@ -12,6 +12,6 @@ struct hpa_hooks_s {
 	uint64_t (*ms_since)(nstime_t *r_time);
 };
 
-extern hpa_hooks_t hpa_hooks_default;
+extern const hpa_hooks_t hpa_hooks_default;
 
 #endif /* JEMALLOC_INTERNAL_HPA_HOOKS_H */

include/jemalloc/internal/jemalloc_internal_externs.h

@@ -22,8 +22,8 @@ extern sec_opts_t opt_hpa_sec_opts;
 extern const char *opt_junk;
 extern bool opt_junk_alloc;
 extern bool opt_junk_free;
-extern void (*junk_free_callback)(void *ptr, size_t size);
-extern void (*junk_alloc_callback)(void *ptr, size_t size);
+extern void (*JET_MUTABLE junk_free_callback)(void *ptr, size_t size);
+extern void (*JET_MUTABLE junk_alloc_callback)(void *ptr, size_t size);
 extern bool opt_utrace;
 extern bool opt_xmalloc;
 extern bool opt_experimental_infallible_new;
@@ -31,7 +31,7 @@ extern bool opt_zero;
 extern unsigned opt_narenas;
 extern zero_realloc_action_t opt_zero_realloc_action;
 extern malloc_init_t malloc_init_state;
-extern const char *zero_realloc_mode_names[];
+extern const char *const zero_realloc_mode_names[];
 extern atomic_zu_t zero_realloc_count;
 extern bool opt_cache_oblivious;
 extern unsigned opt_debug_double_free_max_scan;

include/jemalloc/internal/nstime.h

@@ -56,7 +56,7 @@ enum prof_time_res_e {
 typedef enum prof_time_res_e prof_time_res_t;
 
 extern prof_time_res_t opt_prof_time_res;
-extern const char *prof_time_res_mode_names[];
+extern const char *const prof_time_res_mode_names[];
 
 JEMALLOC_ALWAYS_INLINE void
 nstime_init_zero(nstime_t *time) {

include/jemalloc/internal/pa.h

@@ -131,7 +131,7 @@ pa_shard_ehooks_get(pa_shard_t *shard) {
 
 /* Returns true on error. */
 bool pa_central_init(pa_central_t *central, base_t *base, bool hpa,
-    hpa_hooks_t *hpa_hooks);
+    const hpa_hooks_t *hpa_hooks);
 
 /* Returns true on error. */
 bool pa_shard_init(tsdn_t *tsdn, pa_shard_t *shard, pa_central_t *central,

include/jemalloc/internal/pages.h

@@ -102,7 +102,7 @@ typedef enum {
 #define THP_MODE_DEFAULT thp_mode_default
 extern thp_mode_t opt_thp;
 extern thp_mode_t init_system_thp_mode; /* Initial system wide state. */
-extern const char *thp_mode_names[];
+extern const char *const thp_mode_names[];
 
 void *pages_map(void *addr, size_t size, size_t alignment, bool *commit);
 void pages_unmap(void *addr, size_t size);

src/arena.c

@@ -21,7 +21,7 @@ JEMALLOC_DIAGNOSTIC_DISABLE_SPURIOUS
  * Define names for both unininitialized and initialized phases, so that
  * options and mallctl processing are straightforward.
  */
-const char *percpu_arena_mode_names[] = {
+const char *const percpu_arena_mode_names[] = {
 	"percpu",
 	"phycpu",
 	"disabled",
@@ -37,7 +37,7 @@ static atomic_zd_t dirty_decay_ms_default;
 static atomic_zd_t muzzy_decay_ms_default;
 
 emap_t arena_emap_global;
-pa_central_t arena_pa_central_global;
+static pa_central_t arena_pa_central_global;
 
 div_info_t arena_binind_div_info[SC_NBINS];
 

src/base.c

@@ -22,7 +22,7 @@ static base_t *b0;
 
 metadata_thp_mode_t opt_metadata_thp = METADATA_THP_DEFAULT;
 
-const char *metadata_thp_mode_names[] = {
+const char *const metadata_thp_mode_names[] = {
 	"disabled",
 	"auto",
 	"always"

src/extent_dss.c

@@ -10,7 +10,7 @@
 
 const char	*opt_dss = DSS_DEFAULT;
 
-const char	*dss_prec_names[] = {
+const char	*const dss_prec_names[] = {
 	"disabled",
 	"primary",
 	"secondary",

src/hpa_hooks.c

@@ -11,7 +11,7 @@ static void hpa_hooks_dehugify(void *ptr, size_t size);
 static void hpa_hooks_curtime(nstime_t *r_nstime, bool first_reading);
 static uint64_t hpa_hooks_ms_since(nstime_t *past_nstime);
 
-hpa_hooks_t hpa_hooks_default = {
+const hpa_hooks_t hpa_hooks_default = {
 	&hpa_hooks_map,
 	&hpa_hooks_unmap,
 	&hpa_hooks_purge,

src/jemalloc.c

@@ -121,7 +121,7 @@ zero_realloc_action_t opt_zero_realloc_action =
 
 atomic_zu_t zero_realloc_count = ATOMIC_INIT(0);
 
-const char *zero_realloc_mode_names[] = {
+const char *const zero_realloc_mode_names[] = {
 	"alloc",
 	"free",
 	"abort",
@@ -142,8 +142,8 @@ static void default_junk_free(void *ptr, size_t usize) {
 	memset(ptr, junk_free_byte, usize);
 }
 
-void (*junk_alloc_callback)(void *ptr, size_t size) = &default_junk_alloc;
-void (*junk_free_callback)(void *ptr, size_t size) = &default_junk_free;
+void (*JET_MUTABLE junk_alloc_callback)(void *ptr, size_t size) = &default_junk_alloc;
+void (*JET_MUTABLE junk_free_callback)(void *ptr, size_t size) = &default_junk_free;
 
 bool	opt_utrace = false;
 bool	opt_xmalloc = false;
@@ -158,7 +158,7 @@ unsigned opt_debug_double_free_max_scan =
     SAFETY_CHECK_DOUBLE_FREE_MAX_SCAN_DEFAULT;
 
 /* Protects arenas initialization. */
-malloc_mutex_t arenas_lock;
+static malloc_mutex_t arenas_lock;
 
 /* The global hpa, and whether it's on. */
 bool opt_hpa = false;

src/nstime.c

@@ -228,7 +228,7 @@ nstime_monotonic_t *JET_MUTABLE nstime_monotonic = nstime_monotonic_impl;
 prof_time_res_t opt_prof_time_res =
 	prof_time_res_default;
 
-const char *prof_time_res_mode_names[] = {
+const char *const prof_time_res_mode_names[] = {
 	"default",
 	"high",
 };

src/pa.c

@@ -17,7 +17,7 @@ pa_nactive_sub(pa_shard_t *shard, size_t sub_pages) {
 
 bool
 pa_central_init(pa_central_t *central, base_t *base, bool hpa,
-    hpa_hooks_t *hpa_hooks) {
+    const hpa_hooks_t *hpa_hooks) {
 	bool err;
 	if (hpa) {
 		err = hpa_central_init(&central->hpa, base, hpa_hooks);

src/pages.c

@@ -42,7 +42,7 @@ static int	mmap_flags;
 #endif
 static bool	os_overcommits;
 
-const char *thp_mode_names[] = {
+const char *const thp_mode_names[] = {
 	"default",
 	"always",
 	"never",

src/prof.c

@@ -73,16 +73,16 @@ static malloc_mutex_t next_thr_uid_mtx;
 bool prof_booted = false;
 
 /* Logically a prof_backtrace_hook_t. */
-atomic_p_t prof_backtrace_hook;
+static atomic_p_t prof_backtrace_hook;
 
 /* Logically a prof_dump_hook_t. */
-atomic_p_t prof_dump_hook;
+static atomic_p_t prof_dump_hook;
 
 /* Logically a prof_sample_hook_t. */
-atomic_p_t prof_sample_hook;
+static atomic_p_t prof_sample_hook;
 
 /* Logically a prof_sample_free_hook_t. */
-atomic_p_t prof_sample_free_hook;
+static atomic_p_t prof_sample_free_hook;
 
 /******************************************************************************/
 

src/prof_log.c

@@ -25,7 +25,7 @@ enum prof_logging_state_e {
  * - started: log_start called, log_stop not called yet. Allocations are logged.
  * - dumping: log_stop called but not finished; samples are not logged anymore.
  */
-prof_logging_state_t prof_logging_state = prof_logging_state_stopped;
+static prof_logging_state_t prof_logging_state = prof_logging_state_stopped;
 
 /* Used in unit tests. */
 static bool prof_log_dummy = false;

src/prof_sys.c

@@ -27,8 +27,6 @@
 
 malloc_mutex_t prof_dump_filename_mtx;
 
-bool prof_do_mock = false;
-
 static uint64_t prof_dump_seq;
 static uint64_t prof_dump_iseq;
 static uint64_t prof_dump_mseq;

src/stats.c

@@ -9,13 +9,13 @@
 #include "jemalloc/internal/mutex_prof.h"
 #include "jemalloc/internal/prof_stats.h"
 
-const char *global_mutex_names[mutex_prof_num_global_mutexes] = {
+static const char *const global_mutex_names[mutex_prof_num_global_mutexes] = {
 #define OP(mtx) #mtx,
 	MUTEX_PROF_GLOBAL_MUTEXES
 #undef OP
 };
 
-const char *arena_mutex_names[mutex_prof_num_arena_mutexes] = {
+static const char *const arena_mutex_names[mutex_prof_num_arena_mutexes] = {
 #define OP(mtx) #mtx,
 	MUTEX_PROF_ARENA_MUTEXES
 #undef OP

test/unit/hpa.c

@@ -37,7 +37,7 @@ static hpa_shard_opts_t test_hpa_shard_opts_default = {
 };
 
 static hpa_shard_t *
-create_test_data(hpa_hooks_t *hooks, hpa_shard_opts_t *opts) {
+create_test_data(const hpa_hooks_t *hooks, hpa_shard_opts_t *opts) {
 	bool err;
 	base_t *base = base_new(TSDN_NULL, /* ind */ SHARD_IND,
 	    &ehooks_default_extent_hooks, /* metadata_use_hooks */ true);