探究realloc用法，realloc函数对同一个地址重复操作会返回NULL！

Question

一、在程序设计中，某次意外操作realloc操作同一个地址，造成了其返回NULL异常。
realloc传入的指针与pCommandTemp指针所赋值不一致，在第三次realloc时必出现异常，
重启10次，现象稳定。

for(StopActionChild=mxmlFindElement(AutoChild,tree,"command",NULL,NULL,MXML_DESCEND);
                        StopActionChild!=NULL;
                        StopActionChild=StopActionChild->next->next)
                    {
                        pCommandTemp = (CommandInfo_t *)realloc((m_ProcInfos + m_ProcInfoNum)->ProcStopActions,sizeof(CommandInfo_t)*(CommandNum+1));
                        if(!pCommandTemp)
                        {
                            LOG_ERR("[appAutoProcLoadConfig-->realloc] pCommandTemp realloc error.\n");
                            free(m_ProcInfos);
                            m_ProcInfos=NULL;
                            mxmlDelete(tree);                                /*删除xml文件句柄*/
                            fclose(fp);                                        /*关闭文件*/    
                            return -1;
                        }
                        (m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCommands = pCommandTemp;
                        memcpy(((m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCommands+CommandNum)->Name, mxmlElementGetAttr(StopActionChild,"name"),30);
                        memcpy(((m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCommands+CommandNum)->Type, mxmlElementGetAttr(StopActionChild,"type"),30);
                        ((m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCommands+CommandNum)->Tab = atoi(mxmlElementGetAttr(StopActionChild,"tab"));
                        ((m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCommands+CommandNum)->Code = atoi(mxmlElementGetAttr(StopActionChild,"code"));
                        CommandNum++;/*停止动作计数递增*/
                    }
                    (m_ProcInfos+m_ProcInfoNum)->JudgeParamInfos->StopCmdNum = CommandNum;

调试结果：

二、编写独立realloc测试程序，首先malloc一个commad结构体，然后重复用commad地址realloc，会在第三个循环出现异常，重启10次，故障现象稳定。

void exam_01()
{
       CommandInfo_t * pCommandTemp=NULL;
       CommandInfo_t *  command=(CommandInfo_t *  )malloc(sizeof(CommandInfo_t *));
       int i;
       for(i=0;i<100;i++)
        {
              pCommandTemp=(CommandInfo_t *)realloc(command,sizeof(CommandInfo_t )*(i+1));
              LOG_WARN("\n<>realloc test: < pCommandTemp:0x%x,m_ProcInfoNum:%d,CommandNum:%d>
              \n",pCommandTemp,0,i);
             if(!pCommandTemp)
              {
                        LOG_ERR("pCommandTemp realloc error.\n");
                        return;
              }
        }
}

调试结果：

关于realloc对同一个地址重复操作会出现返回NULL结果疑问，目前寻找资料未能找到合理解释，该种现象的原理？

Answer 1