goto指令跳过可变长度数组

Question

int main() {
    int sz = 10; 
    goto end;
    char bytes[sz];
end:
    return 0;
}

我在编译时遇到以下错误.我使用gcc和C99标准.

test.c: In function ‘main’:
test.c:3:2: error: jump into scope of identifier with variably modified type
test.c:5:1: note: label ‘end’ defined here
test.c:4:7: note: ‘bytes’ declared here

Answer 1

标准是禁止的:

C99 standard, paragraph 6.8.6.1

Constraints

[...] A goto statement shall not jump from outside the scope of an identi?er having a 
      variably modi?ed type to inside the scope of that identi?er.

您goto跳过bytes在运行时分配数组的行.这是不允许的.

你可以bytes用花括号来限制它的范围,把分配放在goto和标签之前,或者根本不使用goto.

更明确地说,一旦bytes分配,你现在"在"范围内.在分配之前,您在范围之外.所以你不能"从范围外跳"到"范围内".