The following C++ code, compiles without warning in Visual Studio 2010:
extern void callFunc( int, int );
struct str_wrapper
{
str_wrapper();
};
extern bool tryParseInt( const str_wrappe开发者_如何学编程r& str, int& outValue );
void test()
{
int x, y;
if ( tryParseInt( str_wrapper(), x ) && tryParseInt( str_wrapper(), y ) )
{
// No warning generated
callFunc( x, y );
}
}
However if str_wrapper has a user-defined destructor, the code generates the warning on the callFunc(x, y) line:
- warning C4701: potentially uninitialized local variable 'y' used.
extern void callFunc( int, int );
struct str_wrapper
{
str_wrapper();
~str_wrapper(); ///< Causes warning C4701 below
};
extern bool tryParseInt( const str_wrapper& str, int& outValue );
void test()
{
int x, y;
if ( tryParseInt( str_wrapper(), x ) && tryParseInt( str_wrapper(), y ) )
{
// C4701 generated for following line
callFunc( x, y );
}
}
I would be happy if both examples generated a warning, or if neither example generated a warning. Am I missing some obscure C++ rule, or is this a compiler bug?
Unfortunately I wasn't able to reproduce that warning with provided code. However, I assume the compiler generates it because of a short-circuit evaluation language feature.
X should be always "initialized" in tryParseInt function, but "initialization" of Y depends only on boolean result from previous tryParseInt(str_wrapper(), x) call. But yeah, it still doesn't make any sense why the warning was generated for line inside an if-block. Maybe the compiler has fooled itself?
精彩评论