Add MEM_CUSTOM_ALLOCATOR and make LIBC a subset of it

Allow one to provide a custom implementation of free/malloc/calloc
instead of the lwip internal allocator. The code to use the libc's
implementation already existed, so generalize the existing code and make
the libc variant a specialized case of this new capability, retaining
full backwards compatibility.

src/core/init.c

@@ -196,8 +196,11 @@ PACK_STRUCT_END
 #if (LWIP_ALTCP && LWIP_EVENT_API)
 #error "The application layered tcp API does not work with LWIP_EVENT_API"
 #endif
-#if (MEM_LIBC_MALLOC && MEM_USE_POOLS)
-#error "MEM_LIBC_MALLOC and MEM_USE_POOLS may not both be simultaneously enabled in your lwipopts.h"
+#if (MEM_CUSTOM_ALLOCATOR && !(defined(MEM_CUSTOM_FREE) && defined(MEM_CUSTOM_MALLOC) && defined(MEM_CUSTOM_CALLOC)))
+#error "All of MEM_CUSTOM_FREE/MEM_CUSTOM_MALLOC/MEM_CUSTOM_CALLOC must be provided if MEM_CUSTOM_ALLOCATOR is enabled in your lwipopts.h"
+#endif
+#if (MEM_USE_POOLS && MEM_CUSTOM_ALLOCATOR)
+#error "MEM_USE_POOLS may not be used with a custom allocator (MEM_CUSTOM_ALLOCATOR or MEM_LIBC_MALLOC) enabled in your lwipopts.h"
 #endif
 #if (MEM_USE_POOLS && !MEMP_USE_CUSTOM_POOLS)
 #error "MEM_USE_POOLS requires custom pools (MEMP_USE_CUSTOM_POOLS) to be enabled in your lwipopts.h"

src/core/mem.c

@@ -152,7 +152,7 @@ mem_overflow_init_raw(void *p, size_t size)
 }
 #endif /* MEM_OVERFLOW_CHECK || MEMP_OVERFLOW_CHECK */
 
-#if MEM_LIBC_MALLOC || MEM_USE_POOLS
+#if MEM_CUSTOM_ALLOCATOR || MEM_USE_POOLS
 
 /** mem_init is not used when using pools instead of a heap or using
  * C library malloc().
@@ -172,23 +172,9 @@ mem_trim(void *mem, mem_size_t size)
   LWIP_UNUSED_ARG(size);
   return mem;
 }
-#endif /* MEM_LIBC_MALLOC || MEM_USE_POOLS */
+#endif /* MEM_CUSTOM_ALLOCATOR || MEM_USE_POOLS */
 
-#if MEM_LIBC_MALLOC
-/* lwIP heap implemented using C library malloc() */
-
-/* in case C library malloc() needs extra protection,
- * allow these defines to be overridden.
- */
-#ifndef mem_clib_free
-#define mem_clib_free free
-#endif
-#ifndef mem_clib_malloc
-#define mem_clib_malloc malloc
-#endif
-#ifndef mem_clib_calloc
-#define mem_clib_calloc calloc
-#endif
+#if MEM_CUSTOM_ALLOCATOR
 
 #if LWIP_STATS && MEM_STATS
 #define MEM_LIBC_STATSHELPER_SIZE LWIP_MEM_ALIGN_SIZE(sizeof(mem_size_t))
@@ -207,7 +193,7 @@ mem_trim(void *mem, mem_size_t size)
 void *
 mem_malloc(mem_size_t size)
 {
-  void *ret = mem_clib_malloc(size + MEM_LIBC_STATSHELPER_SIZE);
+  void *ret = MEM_CUSTOM_MALLOC(size + MEM_LIBC_STATSHELPER_SIZE);
   if (ret == NULL) {
     MEM_STATS_INC_LOCKED(err);
   } else {
@@ -234,7 +220,7 @@ mem_free(void *rmem)
   rmem = (u8_t *)rmem - MEM_LIBC_STATSHELPER_SIZE;
   MEM_STATS_DEC_USED_LOCKED(used, *(mem_size_t *)rmem);
 #endif
-  mem_clib_free(rmem);
+  MEM_CUSTOM_FREE(rmem);
 }
 
 #elif MEM_USE_POOLS
@@ -978,14 +964,14 @@ mem_malloc_adjust_lfree:
 
 #endif /* MEM_USE_POOLS */
 
-#if MEM_LIBC_MALLOC && (!LWIP_STATS || !MEM_STATS)
+#if MEM_CUSTOM_ALLOCATOR && (!LWIP_STATS || !MEM_STATS)
 void *
 mem_calloc(mem_size_t count, mem_size_t size)
 {
-  return mem_clib_calloc(count, size);
+  return MEM_CUSTOM_CALLOC(count, size);
 }
 
-#else /* MEM_LIBC_MALLOC && (!LWIP_STATS || !MEM_STATS) */
+#else /* MEM_CUSTOM_ALLOCATOR && (!LWIP_STATS || !MEM_STATS) */
 /**
  * Contiguously allocates enough space for count objects that are size bytes
  * of memory each and returns a pointer to the allocated memory.
@@ -1015,4 +1001,4 @@ mem_calloc(mem_size_t count, mem_size_t size)
   }
   return p;
 }
-#endif /* MEM_LIBC_MALLOC && (!LWIP_STATS || !MEM_STATS) */
+#endif /* MEM_CUSTOM_ALLOCATOR && (!LWIP_STATS || !MEM_STATS) */

src/include/lwip/mem.h

@@ -43,7 +43,7 @@
 extern "C" {
 #endif
 
-#if MEM_LIBC_MALLOC
+#if MEM_CUSTOM_ALLOCATOR
 
 #include "lwip/arch.h"
 

src/include/lwip/opt.h

@@ -245,10 +245,28 @@
 /**
  * MEM_LIBC_MALLOC==1: Use malloc/free/realloc provided by your C-library
  * instead of the lwip internal allocator. Can save code size if you
- * already use it.
+ * already use it. Specialized case of MEM_CUSTOM_ALLOCATOR.
+ * @see MEM_CUSTOM_ALLOCATOR
  */
 #if !defined MEM_LIBC_MALLOC || defined __DOXYGEN__
 #define MEM_LIBC_MALLOC                 0
+#elif MEM_LIBC_MALLOC
+#define MEM_CUSTOM_ALLOCATOR            1
+#define MEM_CUSTOM_FREE                 free
+#define MEM_CUSTOM_MALLOC               malloc
+#define MEM_CUSTOM_CALLOC               calloc
+#endif
+
+/**
+ * MEM_CUSTOM_ALLOCATOR==1: Use malloc/free/realloc provided by a custom
+ * implementation instead of the lwip internal allocator. Can save code size if
+ * you already use it. If enabled, you have to define those functions:
+ *  \#define MEM_CUSTOM_FREE   my_free
+ *  \#define MEM_CUSTOM_MALLOC my_malloc
+ *  \#define MEM_CUSTOM_CALLOC my_calloc
+ */
+#if !defined MEM_CUSTOM_ALLOCATOR || defined __DOXYGEN__
+#define MEM_CUSTOM_ALLOCATOR            0
 #endif
 
 /**
@@ -2238,7 +2256,7 @@
  * MEM_STATS==1: Enable mem.c stats.
  */
 #if !defined MEM_STATS || defined __DOXYGEN__
-#define MEM_STATS                       ((MEM_LIBC_MALLOC == 0) && (MEM_USE_POOLS == 0))
+#define MEM_STATS                       ((MEM_CUSTOM_ALLOCATOR == 0) && (MEM_USE_POOLS == 0))
 #endif
 
 /**