GCC错误：功能可能是候选属性“纯”，如果它被称为正常返回

Question

鉴于此代码：

#include <cstdlib> 

void func(int x) 
{ 
    if (x) 
    abort(); 
}; 

g++ -Werror=suggest-attribute=pure抱怨：

error: function might be candidate for attribute ‘pure’ if it is known to return normally

这似乎很奇怪，以我 - 是不是明显知道该函数不能正常返回？有什么办法可以告诉GCC它并不总是正常返回，或者我不希望这个警告出现在这个特定的函数中？

演示：https://godbolt.org/g/720VOT

Answer 1

这似乎是一个错误在海湾合作委员会（或文档和实际执行的至少差异）。该documentation on -Wsuggest-attribute=pure写着：

-Wsuggest-attribute=pure
-Wsuggest-attribute=const
-Wsuggest-attribute=noreturn

Warn about functions that might be candidates for attributes pure , const or noreturn . The compiler only warns for functions visible in other compilation units or (in the case of pure and const) if it cannot prove that the function returns normally. A function returns normally if it doesn't contain an infinite loop or return abnormally by throwing, calling abort or trapping. This analysis requires option -fipa-pure-const , which is enabled by default at -O and higher. Higher optimization levels improve the accuracy of the analysis.

然而，实际的分析似乎忽略不回电话的可能性，虽然它尊重可能的例外：

$ cat test-noreturn.cpp 
[[noreturn]] void foo(); 

void func(int x) 
{ 
    if (x) 
     foo(); 
} 

$ g++ -std=c++11 -c -O -Wsuggest-attribute=pure test-noreturn.cpp 
$ cat test-noreturn-nothrow.cpp 
[[noreturn]] void foo() throw(); 
//      ^^^^^^^ 

void func(int x) 
{ 
    if (x) 
     foo(); 
} 
$ g++ -std=c++11 -c -O -Wsuggest-attribute=pure test-noreturn-nothrow.cpp 
test-noreturn-nothrow.cpp: In function ‘void func(int)’: 
test-noreturn-nothrow.cpp:4:6: warning: function might be candidate for attribute ‘pure’ if it is known to return normally [-Wsuggest-attribute=pure] 
void func(int x) 
    ^