Comment by david2ndaccount
9 hours ago
> If the compiler supports "-E", there absolutely is some equivalent of the expanded text, with (somewhat limited) whitespace info available: if you insert whitespace into between "b" and the comma in "b,", then "-E" invocation will dutifully show it. Yes, multiple spaces are collapsed into one, but their presence/absence is tracked already.
Whitespace is significant in the preprocessor so of course it tracks whitespace. Whitespace isn’t dropped until phase 7 when pp-tokens are converted to C tokens.
As I said it’s not impossible, write the patch and see if GCC accepts it.
Also the position in the original source code is tracked.
In fact, this enhancement should be doable. Please file a bug. But the answer why something is not done in a C compiler is usually: Nobody did substantial investments on it in the last two decades. So if you want to see improvements, usually one has to submit a patch.