Add optional runtime swappable custom allocator

CMakeLists.txt

@@ -113,6 +113,8 @@ if (NOT WIN32)
     mark_as_advanced(NNG_SETSTACKSIZE)
 endif ()
 
+nng_defines_if(NNG_ENABLE_CUSTOM_ALLOC NNG_ENABLE_CUSTOM_ALLOC)
+
 nng_defines_if(NNG_ENABLE_STATS NNG_ENABLE_STATS)
 
 # IPv6 enable

cmake/NNGOptions.cmake

@@ -39,6 +39,9 @@ option(NNG_ENABLE_COVERAGE "Enable coverage reporting." OFF)
 # for the public library.
 option(NNG_ELIDE_DEPRECATED "Elide deprecated functionality." OFF)
 
+option(NNG_ENABLE_CUSTOM_ALLOC "Enable overridable function pointers for allocation functions." OFF)
+mark_as_advanced(NNG_ENABLE_CUSTOM_ALLOC)
+
 option(NNG_ENABLE_STATS "Enable statistics." ON)
 mark_as_advanced(NNG_ENABLE_STATS)
 

include/nng/nng.h

@@ -551,6 +551,10 @@ NNG_DECL int nng_ctx_set_int(nng_ctx, const char *, int);
 NNG_DECL int nng_ctx_set_size(nng_ctx, const char *, size_t);
 NNG_DECL int nng_ctx_set_ms(nng_ctx, const char *, nng_duration);
 
+#ifdef NNG_ENABLE_CUSTOM_ALLOC
+NNG_DECL void nng_alloc_set(void* (*malloc)(size_t), void* (*calloc)(size_t, size_t), void (*free)(void*));
+#endif
+
 // nng_alloc is used to allocate memory.  It's intended purpose is for
 // allocating memory suitable for message buffers with nng_send().
 // Applications that need memory for other purposes should use their platform

src/core/defs.h

@@ -246,6 +246,12 @@ typedef nni_type nni_opt_type;
 #endif // defined(__BYTE_ORDER)
 #endif // defined() endianness
 
+extern void* (*nni_malloc_fn)(size_t);
+
+extern void* (*nni_calloc_fn)(size_t, size_t);
+
+extern void (*nni_free_fn)(void*);
+
 // nni_alloc allocates memory.  In most cases this can just be malloc().
 // However, you may provide a different allocator, for example it is
 // possible to use a slab allocator or somesuch.  It is permissible for this

src/nng.c

@@ -8,6 +8,7 @@
 // found online at https://opensource.org/licenses/MIT.
 //
 
+#include "core/defs.h"
 #include "core/nng_impl.h"
 #include "core/pipe.h"
 #include "core/platform.h"
@@ -47,6 +48,24 @@ nng_socket_id(nng_socket s)
 	return (((int) s.id > 0) ? (int) s.id : -1);
 }
 
+#ifdef NNG_ENABLE_CUSTOM_ALLOC
+void
+nng_alloc_set(void* (*malloc)(size_t), void* (*calloc)(size_t, size_t), void (*free)(void*))
+{
+	if (malloc) {
+		nni_malloc_fn = malloc;
+	}
+
+	if (calloc) {
+		nni_calloc_fn = calloc;
+	}
+
+	if (free) {
+		nni_free_fn = free;
+	}
+}
+#endif
+
 void *
 nng_alloc(size_t sz)
 {

src/platform/posix/posix_alloc.c

@@ -13,24 +13,34 @@
 
 #include <stdlib.h>
 
+#ifdef NNG_ENABLE_CUSTOM_ALLOC
+void* (*nni_malloc_fn)(size_t) = malloc;
+void* (*nni_calloc_fn)(size_t, size_t) = calloc;
+void (*nni_free_fn)(void*) = free;
+#else
+#define nni_malloc_fn malloc
+#define nni_calloc_fn calloc
+#define nni_free_fn free
+#endif
+
 // POSIX memory allocation.  This is pretty much standard C.
 void *
 nni_alloc(size_t sz)
 {
-	return (sz > 0 ? malloc(sz) : NULL);
+	return (sz > 0 ? nni_malloc_fn(sz) : NULL);
 }
 
 void *
 nni_zalloc(size_t sz)
 {
-	return (sz > 0 ? calloc(1, sz) : NULL);
+	return (sz > 0 ? nni_calloc_fn(1, sz) : NULL);
 }
 
 void
 nni_free(void *ptr, size_t size)
 {
 	NNI_ARG_UNUSED(size);
-	free(ptr);
+	nni_free_fn(ptr);
 }
 
 #endif // NNG_PLATFORM_POSIX

src/platform/windows/win_thread.c

@@ -36,23 +36,33 @@ static pfnSetThreadDescription set_thread_desc;
 
 #include <stdlib.h>
 
+#ifdef NNG_ENABLE_CUSTOM_ALLOC
+void* (*nni_malloc_fn)(size_t) = malloc;
+void* (*nni_calloc_fn)(size_t, size_t) = calloc;
+void (*nni_free_fn)(void*) = free;
+#else
+#define nni_malloc_fn malloc
+#define nni_calloc_fn calloc
+#define nni_free_fn free
+#endif
+
 void *
 nni_alloc(size_t sz)
 {
-	return (sz > 0 ? malloc(sz) : NULL);
+	return (sz > 0 ? nni_malloc_fn(sz) : NULL);
 }
 
 void *
 nni_zalloc(size_t sz)
 {
-	return (sz > 0 ? calloc(1, sz) : NULL);
+	return (sz > 0 ? nni_calloc_fn(1, sz) : NULL);
 }
 
 void
 nni_free(void *b, size_t z)
 {
 	NNI_ARG_UNUSED(z);
-	free(b);
+	nni_free_fn(b);
 }
 
 void