Strange interaction with standard headers in C99 mode with GCC

I was having trouble getting swrap to compile in C99 mode with GCC, but then I put

#undef _DEFAULT_SOURCE
#define _DEFAULT_SOURCE 1

at the top of a .c file that #includes swrap.h and it worked. Sources: 1 2

When something like stdio.h is included, it doesn't work by simply putting the snippet in or directly above the #include of swrap.h. You have to put the snippet above all includes in the translation unit to be safe.

I have attached a test case. Try compiling it both ways.
swrap_c_test.zip

[BareRose]

Neat, will have a closer look at that weirdness when I can. Hopefully a solution can be found that won't require awkwardly redefining _DEFAULT_SOURCE everywhere.

What version of GCC and what specific OS are you using BTW?

I don't have it in front of me, but it's Ubuntu 18.04. `_DEFAULT_SOURCE` was defined in ~2015 I think.

…

On September 5, 2019 11:05:15 PM MDT, BareRose ***@***.***> wrote: Neat, will have a closer look at that weirdness when I can. Hopefully a solution can be found that won't require awkwardly redefining `_DEFAULT_SOURCE` everywhere. What version of GCC and what specific OS are you using BTW? -- You are receiving this because you authored the thread. Reply to this email directly or view it on GitHub: #4 (comment)

GCC 7.4.0. But I'm not sure if this is a bug in GCC; it also fails with Clang. Clang does use GCC headers though, so maybe.

It compiles just fine with TCC, and I don't know where TCC's headers come from on Linux. TCC is more of a pure C compiler that I have a fondness for, but it has to work in GCC and Clang.