__COUNTER__ macro not handled properly across #include boundaries

[JoshMcguigan]

Observed behavior

Describe what happened. Any aids you can include (that you think could be relevant) are a tremendous help.

• compile_commands.json or .ccls
  • None
• Reduce to A minimal set of .c .cc .h .hh files that can still demonstrate the issue.

// foo.h

#define CONCAT_IMPL(x, y) x##y
#define MACRO_CONCAT(x, y) CONCAT_IMPL(x, y)

#define FOO typedef int MACRO_CONCAT(foo_, __COUNTER__)

FOO; // defines foo_0
FOO; // defines foo_1

// 01-01.c

#include "foo.h"

FOO; // should define foo 2
FOO; // should define foo 3

foo_0 a;
foo_1 b;
foo_2 c;
foo_3 d;

int main() {
    return 0;
}

• Consider a screencast gif.

ccls reports unknown type name foo_2 and unknown type name foo_3.

Expected behavior

No errors should be reported. ccls should recognize types foo_2 and foo_3, by processing the __COUNTER__ macro in the same way as clang:

$ clang 01-01.c -E 
# 1 "01-01.c"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 348 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "01-01.c" 2
# 1 "./foo.h" 1

typedef int foo_0;
typedef int foo_1;
# 2 "01-01.c" 2

typedef int foo_2;
typedef int foo_3;

foo_0 a;
foo_1 b;
foo_2 c;
foo_3 d;

int main() {
 return 0;
}

Steps to reproduce

1. Copy the c and h file above into a directory and start ccls
2. Select foo_2 to see the diagnostic

System information

• ccls version (git describe --tags --long): ccls-0.20210330-5 (installed via package manager)
• clang version: 13.0.1
• OS: Arch Linux
• Editor: emacs
• Language client (and version): lsp-mode