GCC錯誤：功能可能是候選屬性「純」，如果它被稱爲正常返回

Question

鑑於此代碼：

#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

這似乎很奇怪，以我 - 是不是明顯知道該函數不能正常返回？有什麼辦法可以告訴GCC它並不總是正常返回，或者我不希望這個警告出現在這個特定的函數中？

演示：https://godbolt.org/g/720VOT

Answer 1

這似乎是一個錯誤在海灣合作委員會（或文檔和實際執行的至少差異）。該documentation on -Wsuggest-attribute=pure寫着：

-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，實際的分析似乎忽略不回電話的可能性，雖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) 
    ^