Build Error on Cygwin

[rkaminsk]

Describe the bug
A clear and concise description of what the bug is.

I get the following error using gcc 11.3.0 on cygwin:

/cygdrive/c/projects/clingo/third_party/catch/src/catch2/../catch2/catch_tostring.hpp:214:33: error: there are no arguments to 'strnlen' that depend on a template parameter, so a declaration of 'strnlen' must be available [-fpermissive]
  214 |                 StringRef( str, strnlen( str, SZ ) ) );

What about using strnlen_s instead? The only problem I see is that additional macros would have to be defined but since the templates are fully instantiated, the required code could be moved to the source file.

There might also be another header providing a strnlen. I could dig a little deeper if help is required.

Platform information:

• OS: Windows + Cygwin
• Compiler+version: GCC v11.3.0
• Catch version: v3.1.0

[rkaminsk]

I just saw that this has already been reported in #2511.

[rkaminsk]

Just a simple workaround that could easily be extended to other platforms:

inline std::size_t catch_strnlen(const char *str, std::size_t n)
{
#ifdef __CYGWIN__
    if (str == nullptr || n == 0) {
        return 0;
    }

    std::size_t len = 0;
    while (len < n && str[len] != '\0') {
        ++len;
    }

    return len;
#else
    return strnlen(str, n);
#endif
}

[dimztimz]

There is a better solution with memchr() or with its C++ equivalent std::char_traits::find().

[rkaminsk]

So then this can be written portably in C++11 using

inline std::size_t catch_strnlen(const char *str, std::size_t n)
{
    auto ret = std::memchr(str, '\0', n);
    if (ret != nullptr) {
        return ret - str;
    }
    return n;
}

without resorting to macros.

[neheb]

you sure it's not hidden behind _GNU_SOURCE?

[rkaminsk]

you sure it's not hidden behind _GNU_SOURCE?

It is part of the strings library: https://en.cppreference.com/w/cpp/string/byte/memchr.