如何使用 static 分析工具或编译器标志检测 C++ 代码中的“显式类型转换中的潜在精度损失”

Question

For example:

    long long a = ....;
    int b;
    b = (int) a;

Is there a gcc flag or static analysis tools like Sonarqube can detect this case?

Answer 1

Searching for explicit type castings is a strange task. The developer obviously meant that he wanted to "cut off" high bits using explicit type casting. Nevertheless, I would venture to say that the task was actually different: one had to port a 32-bit application to the 64-bit platform. In this case, yes, it is a very relevant task to detect dangerous explicit types castings. If it is so, there is a solution. There is a special set of diagnostics related to porting in the PVS-Studio analyzer. Examples:

• V202 . Explicit conversion from memsize type to 32-bit integer type.
• V220 . Suspicious sequence of types castings: memsize -> 32-bit integer -> memsize.
• V221 . Suspicious sequence of types castings: pointer -> memsize -> 32-bit integer.
• and others .

Answer 2

You can also try CppDepend which uses Clang as a C/C++ parser, and Clang detects such issues.