clang-tidy modernize-use-default-member-init false negatives

[nick-potenski]

clang-tidy's modernize-use-default-member-init check will ignore constructor member initializers that either directly or indirectly use mathematical operations or casting. For instance, the following code only generates a warning for struct member a. Live example in compiler explorer here: https://godbolt.org/z/9E7Pv5jfa.

#define THE_ANSWER (44 - 2)

struct Bar {
    Bar() : a{0}, b{1 + 1}, c{THE_ANSWER}, d{static_cast<unsigned int>(-1)} {}
    int a;
    int b;
    int c;
    unsigned int d;
};

[<source>:5:9: warning: use default member initializer for 'a' [modernize-use-default-member-init]](javascript:;)
    4 |     Bar() : a{0}, b{1 + 1}, c{THE_ANSWER}, d{static_cast<unsigned int>(-1)} {}
      |             ~~~~
    5 |     int a;
      |         ^
      |          {0}
1 warning generated.

[llvmbot]

@llvm/issue-subscribers-clang-tidy

Author: Nick Potenski (nick-potenski)

clang-tidy's modernize-use-default-member-init check will ignore constructor member initializers that either directly or indirectly use mathematical operations or casting. For instance, the following code only generates a warning for struct member `a`. Live example in compiler explorer here: https://godbolt.org/z/9E7Pv5jfa.

#define THE_ANSWER (44 - 2)

struct Bar {
    Bar() : a{0}, b{1 + 1}, c{THE_ANSWER}, d{static_cast<unsigned int>(-1)} {}
    int a;
    int b;
    int c;
    unsigned int d;
};

[<source>:5:9: warning: use default member initializer for 'a' [modernize-use-default-member-init]](javascript:;)
    4 |     Bar() : a{0}, b{1 + 1}, c{THE_ANSWER}, d{static_cast<unsigned int>(-1)} {}
      |             ~~~~
    5 |     int a;
      |         ^
      |          {0}
1 warning generated.

[nick-potenski]

Also seems to ignore members initialized with static const or static constexpr members:

struct Bar {
    Bar()
        : a{0},
          b{1 + 1},
          c{smAConstantValue},
          d{static_cast<unsigned int>(-1)} {}

    static constexpr int smAConstantValue{3};

    int a;
    int b;
    int c;
    unsigned int d;
};

[<source>:12:9: warning: use default member initializer for 'a' [modernize-use-default-member-init]](javascript:;)
    5 |         : a{0},
      |           ~~~~
    6 |           b{1 + 1},
    7 |           c{smAConstantValue},
    8 |           d{static_cast<unsigned int>(-1)} {}
    9 | 
   10 |     static constexpr int smAConstantValue{3};
   11 | 
   12 |     int a;
      |         ^
      |          {0}
1 warning generated.