Added MEM_LIBC_MALLOC option as workaround for failing mem_malloc().

src/include/lwip/mem.h

@@ -43,12 +43,19 @@ typedef u16_t mem_size_t;
 #define MEM_SIZE_F U16_F
 #endif /* MEM_SIZE > 64000 */
 
-
+#if MEM_LIBC_MALLOC
+/* aliases for C library malloc() */
+#define mem_init()
+#define mem_free(x) free(x)
+#define mem_malloc(x) malloc(x)
+#define mem_realloc(x, size) realloc(x,size)
+#else
+/* lwIP alternative malloc */
 void mem_init(void);
-
 void *mem_malloc(mem_size_t size);
 void mem_free(void *mem);
 void *mem_realloc(void *mem, mem_size_t size);
+#endif
 
 #ifndef MEM_ALIGN_SIZE
 #define MEM_ALIGN_SIZE(size) (((size) + MEM_ALIGNMENT - 1) & ~(MEM_ALIGNMENT-1))

src/include/lwip/opt.h

@@ -53,6 +53,10 @@
 #define NO_SYS                          0
 #endif
 /* ---------- Memory options ---------- */
+#ifndef MEM_LIBC_MALLOC
+#define MEM_LIBC_MALLOC                 0
+#endif
+
 /* MEM_ALIGNMENT: should be set to the alignment of the CPU for which
    lwIP is compiled. 4 byte alignment -> define MEM_ALIGNMENT to 4, 2
    byte alignment -> define MEM_ALIGNMENT to 2. */