avoid trying to use mremap outside of Linux

h_malloc.c

@@ -1416,6 +1416,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
                 return old;
             }
 
+#ifdef HAVE_COMPATIBLE_MREMAP
             static const bool vma_merging_reliable = false;
             if (vma_merging_reliable) {
                 // in-place growth
@@ -1465,6 +1466,7 @@ EXPORT void *h_realloc(void *old, size_t size) {
                 thread_seal_metadata();
                 return new;
             }
+#endif
         }
     }
 

memory.c

@@ -68,6 +68,7 @@ int memory_protect_rw_metadata(void *ptr, size_t size) {
     return memory_protect_prot(ptr, size, PROT_READ|PROT_WRITE, get_metadata_key());
 }
 
+#ifdef HAVE_COMPATIBLE_MREMAP
 int memory_remap(void *old, size_t old_size, size_t new_size) {
     void *ptr = mremap(old, old_size, new_size, 0);
     if (unlikely(ptr == MAP_FAILED)) {
@@ -89,6 +90,7 @@ int memory_remap_fixed(void *old, size_t old_size, void *new, size_t new_size) {
     }
     return 0;
 }
+#endif
 
 void memory_set_name(UNUSED void *ptr, UNUSED size_t size, UNUSED const char *name) {
 #ifdef LABEL_MEMORY

memory.h

@@ -3,6 +3,10 @@
 
 #include <stddef.h>
 
+#ifdef __linux__
+#define HAVE_COMPATIBLE_MREMAP
+#endif
+
 int get_metadata_key(void);
 
 void *memory_map(size_t size);
@@ -11,8 +15,10 @@ int memory_unmap(void *ptr, size_t size);
 int memory_protect_ro(void *ptr, size_t size);
 int memory_protect_rw(void *ptr, size_t size);
 int memory_protect_rw_metadata(void *ptr, size_t size);
+#ifdef HAVE_COMPATIBLE_MREMAP
 int memory_remap(void *old, size_t old_size, size_t new_size);
 int memory_remap_fixed(void *old, size_t old_size, void *new, size_t new_size);
+#endif
 void memory_set_name(void *ptr, size_t size, const char *name);
 
 #endif