Bug 21944 – importC: Support parsing # line marker directive extensions

The gcc preprocessor (gcc -E) spits out code like this: --- # 1 "test.c" # 1 "<built-in>" # 1 "<command-line>" # 31 "<command-line>" # 1 "/usr/include/stdc-predef.h" 1 3 4 # 32 "<command-line>" 2 # 1 "test.c" --- The CParser seems to successfully ignore these directives, though it does so using the `panic()` function. However if a line marker appears in the middle of a declaration, e.g: --- struct Foo { int var; #1 "foo.c" 3 4 }; --- An error occurs.

@ibuclaw created dlang/dmd pull request #12585 "fix Issue 21944 - importC: Add `-P` to C preprocessor invocation example" fixing this issue: - fix Issue 21944 - importC: Add `-P` to C preprocessor invocation example The recommendation for using a preprocessor does not generate compilable code due to the `#line` directive not being supported by importC. https://github.com/dlang/dmd/pull/12585

Patch sent that recommends users to use `-P` to turn off the generation of linemarkers in the output from the preprocessor. This saves us having to support the extension.

Fix committed as https://github.com/dlang/dmd/commit/ba38f4bda14b3c92d5ef64d5221366ee7c78d944

Not implementing this would be a nuisance, and there'd be no way to get the line numbers correct for debugging.

The Digital Mars preprocessor, as well as the Warp preprocessor, emit linemarker directives.

@WalterBright created dlang/dmd pull request #12637 "fix Issue 21944 - ImportC: Support parsing # line marker directive ex…" fixing this issue: - fix Issue 21944 - importC: Support parsing # line marker directive extensions https://github.com/dlang/dmd/pull/12637

dlang/dmd pull request #12637 "fix Issue 21944 - ImportC: Support parsing # line marker directive ex…" was merged into master: - 4423156fdd66cdd5bbc4233bd85add1b8ea68d78 by Walter Bright: fix Issue 21944 - importC: Support parsing # line marker directive extensions https://github.com/dlang/dmd/pull/12637