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LwIP中发送小数据可以，发送140个字节的数据发送失败，查找原因，是分配内存失败，返回是men->used 为121
按道理说即使分配失败，used返回的数据也是1也不会是121？ mem_malloc(mem_size_t size){ mem_size_t ptr, ptr2; struct mem *mem, *mem2;#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT u8_t local_mem_free_count = 0;#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */ LWIP_MEM_ALLOC_DECL_PROTECT(); if (size == 0) { return NULL; }printf("size %d n",size); /* Expand the size of the allocated memory region so that we can adjust for alignment. */ size = LWIP_MEM_ALIGN_SIZE(size); if(size < MIN_SIZE_ALIGNED) { /* every data block must be at least MIN_SIZE_ALIGNED long */ size = MIN_SIZE_ALIGNED; } if (size > MEM_SIZE_ALIGNED) { return NULL; } /* protect the heap from concurrent access */ sys_arch_sem_wait(mem_sem, 0); LWIP_MEM_ALLOC_PROTECT();#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT /* run as long as a mem_free disturbed mem_malloc */ do { local_mem_free_count = 0;#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */ /* Scan through the heap searching for a free block that is big enough, * beginning with the lowest free block. */ for (ptr = (u8_t *)lfree - ram; ptr < MEM_SIZE_ALIGNED - size; ptr = ((struct mem *)&ram[ptr])->next) { mem = (struct mem *)&ram[ptr];#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT mem_free_count = 0; LWIP_MEM_ALLOC_UNPROTECT(); /* allow mem_free to run */ LWIP_MEM_ALLOC_PROTECT(); if (mem_free_count != 0) { local_mem_free_count = mem_free_count; } mem_free_count = 0;#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */printf("mem->used %d n",mem->used); if ((!mem->used) && (mem->next - (ptr + SIZEOF_STRUCT_MEM)) >= size) { /* mem is not used and at least perfect fit is possible: * mem->next - (ptr + SIZEOF_STRUCT_MEM) gives us the 'user data size' of mem */ if (mem->next - (ptr + SIZEOF_STRUCT_MEM) >= (size + SIZEOF_STRUCT_MEM + MIN_SIZE_ALIGNED)) { /* (in addition to the above, we test if another struct mem (SIZEOF_STRUCT_MEM) containing * at least MIN_SIZE_ALIGNED of data also fits in the 'user data space' of 'mem') * -> split large block, create empty remainder, * remainder must be large enough to contain MIN_SIZE_ALIGNED data: if * mem->next - (ptr + (2*SIZEOF_STRUCT_MEM)) == size, * struct mem would fit in but no data between mem2 and mem2->next * @todo we could leave out MIN_SIZE_ALIGNED. We would create an empty * region that couldn't hold data, but when mem->next gets freed, * the 2 regions would be combined, resulting in more free memory */ ptr2 = ptr + SIZEOF_STRUCT_MEM + size; /* create mem2 struct */ mem2 = (struct mem *)&ram[ptr2]; mem2->used = 0; mem2->next = mem->next; mem2->prev = ptr; /* and insert it between mem and mem->next */ mem->next = ptr2; mem->used = 1; if (mem2->next != MEM_SIZE_ALIGNED) { ((struct mem *)&ram[mem2->next])->prev = ptr2; } MEM_STATS_INC_USED(used, (size + SIZEOF_STRUCT_MEM)); } else { /* (a mem2 struct does no fit into the user data space of mem and mem->next will always * be used at this point: if not we have 2 unused structs in a row, plug_holes should have * take care of this). * -> near fit or excact fit: do not split, no mem2 creation * also can't move mem->next directly behind mem, since mem->next * will always be used at this point! */ mem->used = 1; MEM_STATS_INC_USED(used, mem->next - ((u8_t *)mem - ram)); } if (mem == lfree) { /* Find next free block after mem and update lowest free pointer */ while (lfree->used && lfree != ram_end) { LWIP_MEM_ALLOC_UNPROTECT(); /* prevent high interrupt latency... */ LWIP_MEM_ALLOC_PROTECT(); lfree = (struct mem *)&ram[lfree->next]; } LWIP_ASSERT("mem_malloc: !lfree->used", ((lfree == ram_end) || (!lfree->used))); } LWIP_MEM_ALLOC_UNPROTECT(); sys_sem_signal(mem_sem); LWIP_ASSERT("mem_malloc: allocated memory not above ram_end.", (mem_ptr_t)mem + SIZEOF_STRUCT_MEM + size <= (mem_ptr_t)ram_end); LWIP_ASSERT("mem_malloc: allocated memory properly aligned.", ((mem_ptr_t)mem + SIZEOF_STRUCT_MEM) % MEM_ALIGNMENT == 0); LWIP_ASSERT("mem_malloc: sanity check alignment", (((mem_ptr_t)mem) & (MEM_ALIGNMENT-1)) == 0); return (u8_t *)mem + SIZEOF_STRUCT_MEM; } }#if LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT /* if we got interrupted by a mem_free, try again */ } while(local_mem_free_count != 0);#endif /* LWIP_ALLOW_MEM_FREE_FROM_OTHER_CONTEXT */ LWIP_DEBUGF(MEM_DEBUG | LWIP_DBG_LEVEL_SERIOUS, ("mem_malloc: could not allocate %"S16_F" bytesn", (s16_t)size)); MEM_STATS_INC(err); LWIP_MEM_ALLOC_UNPROTECT(); sys_sem_signal(mem_sem); return NULL;} #endif /* MEM_USE_POOLS */ 
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6个回答
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是不是字节没有对齐？
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可否设置内存分配范围大一点？能否解决？
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也配置了啊，如果虚拟140个字节，最后形成包是212个字节，是可以发送的，并且与上位机通信正常 但是，如果使用485，从控制器获取数据140个字节，再把获取的通过TCP发送出去，就发不出去了，但是20个字节可以，最想不明白的是used应该是1或0 ，而现在却是121，不知道这个数据怎么出现。 整个系统设计如下 |
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感谢原子哥，问题已解决，原因是定义了这样几个数组MODBUS_RECEIVE_SBUF[]，影响了协议栈的内存，导致数据出错，内存泄露！改正方法是MODBUS_RECEIVE_SBUF[确定值]！
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