I recently had a bug in a similar context to next one:
double getSomeValue()
{
return 4.0;
}
...
std::string str;
str = getSomeValue();
As you can see here is easy to spot the problem, but in a large code base where getSomeValue()
is not in the same file with the calling code it might be difficult to spot this double
to std::string
silent conversion. GCC compiles this code fine with -Wall -Wextra -Werror
(sample output here, I don't know what warning flags were used: http://ideone.com/BTXBFk ).
How may I force GCC to emit warnings for these dangerous implicit conversions? I tried -Wconversion
, but it is very strict and it causes errors in most included headers for common cases like unsigned - 1
. Is there a weaker version of -Wconversion
?
You can use the -Wfloat-conversion
flag, or the broader -Wconversion
.
However, note that with C++11 uniform initialization brace syntax , you get a warning "out of the box", without the -Wconversion
flag; eg:
#include <string>
double getSomeValue() {
return 4.0;
}
int main() {
std::string str{ getSomeValue() }; // C++11 brace-init
}
C:\\Temp\\CppTests>g++ -std=c++11 test.cpp test.cpp: In function 'int main()': test.cpp:8:35: warning: narrowing conversion of 'getSomeValue()' from 'double' t o 'char' inside { } [-Wnarrowing] std::string str{ getSomeValue() }; ^
您可以使用-Wconversion
并避免错误unsigned - 1
与-Wno-sign-conversion
,如规定在这里 。
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