c - _Static_assert 与 __has_include

Question

我想制作宏，检查文件是否“可包含”。像这样:

#define CHECK(__file)    \
    _Static_assert( __has_include(__file), "Error")
CHECK("header.h");

但它会产生如下错误

f.c:28:3: __has_include must be used within a preprocessing directive
f.c:28:3: Implicit declaration of function '__has_include' is invalid in C99
f.c:28:3: Static_assert expression is not an integral constant expression

这可能吗？或者可能有不同的解决方案会产生类似的结果？

感谢您的帮助!

Answer 1

如果一切都失败了(你很难反驳:“__has_include 必须在预处理指令中使用”)，在它上面抛出另一层间接:

h_assert(){
    for h; do
printf '
#if !__has_include("%s")
_Static_assert(0,"__has_include(\"%s\")");
#endif
' "$h" "$h"
    done
}
h_assert foo.h bar.h baz.h #Generate the header assertions with a POSIX shell