error: suggest parentheses around assignment used as truth value

GCC编译错误解析
最新推荐文章于 2024-03-27 12:38:41 发布
原创 最新推荐文章于 2024-03-27 12:38:41 发布 · 1.6k 阅读 · 0 ·
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本文介绍了一个GCC编译过程中常见的错误：建议在作为布尔值使用的赋值操作周围加上括号。通过一个具体的代码示例解释了如何区分赋值运算符(=)与相等比较运算符(==)，并给出了正确的修改方法。

代码如下：

if(res = em3071_check_and_clear_intr(client))
{
APS_ERR("check/clear intr: %d\n", res);
//    return res;
}

编译报错如下： 

error: suggest parentheses around assignment used as truth value [-Werror=parentheses]

  if(res = em3071_check_and_clear_intr(client))

解决：

gcc编译器要求明确地告诉它是"="还是"=="

if(res == em3071_check_and_clear_intr(client))
{
APS_ERR("check/clear intr: %d\n", res);
//    return res;
}


C: warning: suggest parentheses around assignment used as truth value [-Wparentheses]
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../../bcmdrivers/broadcom/net/wl/bcm96764/main/components/router/hnd_wl//../../../../main/src/wl/sys/wlc_widswips.c:1770:5: error: suggest parentheses around assignment used as truth value [-Werror=parentheses] 1770 | if(cnt4 = bcm_find_tlv_count(body, body_len, DOT11_MNG_HT_CAP)){ | ^~~~
最新发布
10-30
../../bcmdrivers/broadcom/net/wl/bcm96764/main/components/router/hnd_wl//../../../../main/src/wl/sys/wlc_widswips.c:1770:5: error: suggest parentheses around assignment used as truth value [-Werror=...
../../libraries/AP_ToshibaCAN/AP_ToshibaCAN.cpp:163:31: error: suggest parentheses around assignment used as truth value [-Werror=parentheses] 163 | if (recv_frame.id = MOTOR_DATA1) { | ~~~~~~~~~~~~~~^~~~~~~~~~~~~ compilation terminated due to -Wfatal-errors. cc1plus: all warnings being treated as errors
03-15
根据用户提供的信息，错误出现在AP_ToshibaCAN.cpp的第163行，提示“suggest parentheses around assignment used as truth value [-Werror=parentheses]”。然后因为使用了-Wfatal-errors选项，导致编译终止。 ...
http.c:233:17: warning: unused variable ‘pool’ [-Wunused-variable] 233 | ThreadPool *pool = (ThreadPool *)arg; | ^~~~ http.c: In function ‘cgi_execute’: http.c:452:16: warning: suggest parentheses around assignment used as truth value [-Wparentheses] 452 | while (bytes_read = get_line(client, buf, sizeof(buf))) | ^~~~~~~~~~ http.c:473:16: warning: suggest parentheses around assignment used as truth value [-Wparentheses] 473 | while (bytes_read = get_line(client, buf, sizeof(buf))) | ^~~~~~~~~~ http.c:534:35: warning: implicit declaration of function ‘MIN’ [-Wimplicit-function-declaration] 534 | ssize_t to_read = MIN(sizeof(buffer), content_length - total_written); | ^~~ /usr/bin/ld: /tmp/ccaBaF6n.o: in function `cgi_execute': http.c:(.text+0x96f): undefined reference to `MIN' collect2: error: ld returned 1 exit status make: *** [makefile:9: httpd] Error 1
08-15
error_request(client); return; } } else { // 修改为：while ((bytes_read = get_line(...)) > 0) while ((bytes_read = get_line(client, buf, sizeof(buf))) > 0) { if (buf[0] == '\n') { break; ...
#include <bits/stdc++.h> using namespace std; //给定一个整数x判断他的正负如果x>0输出1如果x=0输出0如果x<0输出-1 int main(void) { int x; cin>>n; if(x>0){ count<<"1"; } if(x=0){ count<<"0"; } if(x<0){ count<<"-1"; } return 0; }a.cpp: In function ‘int main()’: a.cpp:7:10: error: ‘n’ was not declared in this scope 7 | cin>>n; | ^ a.cpp:9:14: error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘const char [2]’ to binary ‘operator<<’ 9 | count<<"1"; | ~~~~~^~~~~ a.cpp:11:9: warning: suggest parentheses around assignment used as truth value [-Wparentheses] 11 | if(x=0){ | ~^~ a.cpp:12:14: error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘const char [2]’ to binary ‘operator<<’ 12 | count<<"0"; | ~~~~~^~~~~ a.cpp:15:14: error: invalid operands of types ‘<unresolved overloaded function type>’ and ‘const char [3]’ to binary ‘operator<<’ 15 | count<<"-1"; | ~~~~~^~~~~~
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if ((num = get_value())) { ... } // ✅ ``` **原理**：编译器认为单等号可能是误操作（引用[1]类型安全原则） ### 完整代码示例 ```cpp #include int main() { int num; // ✅ 变量声明 std::cout 输入整数: ...
``` typedef struct { pthread_mutex_t hLock; volatile int iIsRun; void* (* volatile pfnTask)(void*); //函数指针 void *arg; //任务参数 }Task; typedef struct { pthread_mutex_t StackLock; int iIDStack[MAX_TASK_NUM]; int iTopPointer; }Stack; static Stack g_IDTaskStack; static Task stTaskQueueAry[MAX_TASK_NUM]; //static int iTaskCount = 0; //static pthread_mutex_t stMutexQueue; //static pthread_cond_t stCondQueue; static pthread_t stThreadAry[cmnDfn_WORKING_PTHREAD_NUMBER]; void* PthreadPoolWorker(void* arg) { int iRet = -1; int iTskID = (int)(long)arg; Task *pstTsk = &stTaskQueueAry[iTskID]; while(g_iExit == 0) { LOCK(pstTsk->hLock) { if (pstTsk->iIsRun == 0) { sleep(1); continue; } } iRet = (int)(long)pstTsk->pfnTask(pstTsk->arg); if (iRet = 0) { continue; } LOCK(pstTsk->hLock) { pstTsk->pfnTask = NULL; pstTsk->iIsRun = 0; } LOCK(g_IDTaskStack.StackLock) { g_IDTaskStack.iIDStack[++g_IDTaskStack.iTopPointer] = iTskID; } if(iRet < 0) { break; } } iRet = 0; return (void *)(long)iRet; } int ThreadPoolSubmit(void* (*task)(void*),void* arg,int *piTskID) { //int iLoopNum; int iTskID = 0; /*for(iLoopNum = 0; iLoopNum < MAX_TASK_NUM;iLoopNum++) { if (stTaskQueueAry[iLoopNum].pfnTask == NULL) { break; } } if(iLoopNum >= MAX_TASK_NUM) { return -1; }*/ if(g_IDTaskStack.iTopPointer < 0) { return -1; } LOCK(g_IDTaskStack.StackLock) { iTskID = g_IDTaskStack.iIDStack[g_IDTaskStack.iTopPointer--]; assert(iTskID >= 0 && iTskID < MAX_TASK_NUM); } LOCK(stTaskQueueAry[iTskID].hLock) { stTaskQueueAry[iTskID].pfnTask = task; stTaskQueueAry[iTskID].arg = arg; stTaskQueueAry[iTskID].iIsRun = 1; *piTskID = iTskID; } return 0; } int ThreadPoolInit(void) { int iLoopNum; int iRet = -1; int iTskID = 0; g_IDTaskStack.iTopPointer = -1; for(iLoopNum = 0; iLoopNum < MAX_TASK_NUM; iLoopNum++) { g_IDTaskStack.iIDStack[++g_IDTaskStack.iTopPointer] = iLoopNum; } for(iLoopNum = 0; iLoopNum < MAX_TASK_NUM; iLoopNum++) { if(pthread_mutex_init(&stTaskQueueAry[iLoopNum].hLock,NULL) < 0) { cmn_PrtError("Error in initializing mutex"); } if(pthread_create(&stThreadAry[iLoopNum],NULL,PthreadPoolWorker,(void *)(long)iTskID) != 0) { cmn_PrtError("Error in creating thread"); } stTaskQueueAry[iLoopNum].pfnTask = NULL; stTaskQueueAry[iLoopNum].iIsRun = 0; iTskID++; } iRet = 0; _Exit: return iRet; } int ThreadPoolDestroy(void) { int iLoopNum; int iRet = -1; g_iExit = 1; for(iLoopNum = 0; iLoopNum < MAX_TASK_NUM; iLoopNum++) { pthread_join(stThreadAry[iLoopNum], NULL); } for(iLoopNum = 0; iLoopNum < MAX_TASK_NUM; iLoopNum++) { pthread_mutex_destroy(&stTaskQueueAry[iLoopNum].hLock); } iRet = 0; return iRet; }```error: suggest parentheses around assignment used as truth value [-Werror=parentheses] 52 | if (iRet = 0) | ^~~~
03-19
错误信息是“suggest parentheses around assignment used as truth value [-Werror=parentheses]”，出现在第52行的if语句中：if (iRet = 0)。这个错误是因为在条件判断中使用了赋值操作符=而不是比较操作符==，...
c语言编译错误：warning: suggest parentheses around assignment used as truth value
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