add size field to stats and modify mi_stats_get to check the version

Author: daanx

include/mimalloc-stats.h

@@ -11,7 +11,7 @@ terms of the MIT license. A copy of the license can be found in the file
 #include <mimalloc.h>
 #include <stdint.h>
 
-#define MI_STAT_VERSION   3   // increased on every backward incompatible change
+#define MI_STAT_VERSION   4  // increased on every backward incompatible change
 
 // count allocation over time
 typedef struct mi_stat_count_s {
@@ -73,7 +73,8 @@ typedef struct mi_stat_counter_s {
 
 typedef struct mi_stats_s
 {
-  int version;
+  size_t size;          // size of the mi_stats_t structure 
+  size_t version;       
 
   MI_STAT_FIELDS()
 
@@ -94,7 +95,7 @@ typedef struct mi_stats_s
 extern "C" {
 #endif
 
-mi_decl_export bool  mi_stats_get( size_t stats_size, mi_stats_t* stats ) mi_attr_noexcept;
+mi_decl_export bool  mi_stats_get( mi_stats_t* stats ) mi_attr_noexcept;
 mi_decl_export char* mi_stats_get_json( size_t buf_size, char* buf ) mi_attr_noexcept;    // use mi_free to free the result if the input buf == NULL
 
 #ifdef __cplusplus

src/init.c

@@ -136,7 +136,7 @@ static mi_decl_cache_align mi_tld_t tld_main = {
     0, 0, 0, 0, 0, &mi_subproc_default,
     &tld_main.stats
   }, // segments
-  { MI_STAT_VERSION, MI_STATS_NULL }       // stats
+  { sizeof(mi_stats_t), MI_STAT_VERSION, MI_STATS_NULL }       // stats
 };
 
 mi_decl_cache_align mi_heap_t _mi_heap_main = {
@@ -162,7 +162,7 @@ mi_decl_cache_align mi_heap_t _mi_heap_main = {
 
 bool _mi_process_is_initialized = false;  // set to `true` in `mi_process_init`.
 
-mi_stats_t _mi_stats_main = { MI_STAT_VERSION, MI_STATS_NULL };
+mi_stats_t _mi_stats_main = { sizeof(mi_stats_t), MI_STAT_VERSION, MI_STATS_NULL };
 
 #if MI_GUARDED
 mi_decl_export void mi_heap_guarded_set_sample_rate(mi_heap_t* heap, size_t sample_rate, size_t seed) {

src/stats.c

@@ -474,13 +474,10 @@ mi_decl_export void mi_process_info(size_t* elapsed_msecs, size_t* user_msecs, s
 // Return statistics
 // --------------------------------------------------------
 
-bool mi_stats_get(size_t stats_size, mi_stats_t* stats) mi_attr_noexcept {
-  if (stats == NULL || stats_size == 0) return false;
-  _mi_memzero(stats, stats_size);
-  if (stats_size < sizeof(mi_stats_t)) return false;
-  const size_t size = (stats_size > sizeof(mi_stats_t) ? sizeof(mi_stats_t) : stats_size);
-  _mi_memcpy(stats, &_mi_stats_main, size);
-  stats->version = MI_STAT_VERSION;
+bool mi_stats_get(mi_stats_t* stats) mi_attr_noexcept {
+  if (stats == NULL || stats->size != sizeof(mi_stats_t) || stats->version != MI_STAT_VERSION) return false;
+  _mi_memzero(stats,stats->size);
+  _mi_memcpy(stats, &_mi_stats_main, sizeof(mi_stats_t));
   return true;
 }
 
@@ -584,7 +581,7 @@ char* mi_stats_get_json(size_t output_size, char* output_buf) mi_attr_noexcept {
     if (!mi_heap_buf_expand(&hbuf)) return NULL;
   }
   mi_heap_buf_print(&hbuf, "{\n");
-  mi_heap_buf_print_value(&hbuf, "version", MI_STAT_VERSION);
+  mi_heap_buf_print_value(&hbuf, "stat_version", MI_STAT_VERSION);
   mi_heap_buf_print_value(&hbuf, "mimalloc_version", MI_MALLOC_VERSION);
 
   // process info
@@ -624,5 +621,12 @@ char* mi_stats_get_json(size_t output_size, char* output_buf) mi_attr_noexcept {
   }
   mi_heap_buf_print(&hbuf, "  ]\n");  
   mi_heap_buf_print(&hbuf, "}\n");
-  return hbuf.buf;
+  if (hbuf.used >= hbuf.size) {
+    // failed
+    if (hbuf.can_realloc) { mi_free(hbuf.buf); }
+    return NULL;
+  }
+  else {
+    return hbuf.buf;
+  }
 }