On Wednesday, 3 October 2018 at 20:41:15 UTC, welkam wrote:
This flag blocks compilation and I want to just remove it but since I dont know what it is used for I hesitate. If my attempts were to be successful in compiling dmd with other compilers I would make pull request but now I have more question than answers. What this flag does? Why some files compiled with it and other dont? Why it is added to all compilation targets unconditionally?
A long time ago, D global and static variables worked just like in C/C++, and went in the data segment (i.e. there was one per program). At one point, this was changed, so that they would go into TLS by default (i.e. one per thread), thus making a lot of code that was previously not thread-safe, magically thread-safe. To allow developers who wanted to make sure that their code compiled to exactly the same behavior as before to update their programs easily, this flag was added, so that they could find all the places in their program where the new behavior will take into effect.
Today, it is still useful for finding globals in programs that shouldn't have any. I don't know why it's used in DMD, but that might certainly be the reason, considering there is a long-term ongoing effort to make DMD usable as a library.
The flag otherwise should have no effect on the result of the compilation (i.e. produced object files / binaries), so you can remove it locally. You will probably need to investigate why the compiler you're using doesn't support it (perhaps it's there under another name) - the code for its implementation should still be there, as all of DMD/LDC/GDC use the same frontend.
