g++ variable size array no warning?

问题:

int a; cin >> a; int ints[a]; 

Why does this not throw any kind of warning while compiling? How do I know when this array thing is actually using the heap or the stack?

g++ -std=c++11 -Wall *.cpp -o main

回答1:

ISO C++ disallows the use of variable length arrays, which g++ happily tells you if you increase the strictness of it by passing it the -pedantic flag.

Using -pedantic will issue a warning about things breaking the standard. If you want g++ to issue an error and with this refuse compilation because of such things; use -pedantic-errors.

---

g++ -Wall -pedantic -std=c++11 apa.cpp 

apa.cpp: In function ‘int main(int, char**)’: apa.cpp:8:13: warning: ISO C++ forbids variable length array ‘ints’ [-Wvla]    int ints[a];              ^ apa.cpp:8:7: warning: unused variable ‘ints’ [-Wunused-variable]    int ints[a];        ^ 

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