LibTooling cannot correctly find header files with the same name in different folder when running on multiple source files

[PHIKN1GHT]

If we have a/a.c:

#include "A.h"
#include "stdio.h"
extern void hello_e();
int main() {
  hello_e();
  printf("%f\n", PI);
  return 0;
}

and b/b.c:

#include "A.h"
#include <stdio.h>

void hello_e() { printf("%f\n", M_E); }

and a/aa/A.h

#define PI 3.14

and b/A.h

#include <math.h>
// to use M_E

With a simple compile_commands.json:

[
  {
    "arguments": [
      "/usr/bin/gcc",
      "-c",
      "-o",
      "b",
      "b.c"
    ],
    "directory": "/home/me/testcase/b",
    "file": "/home/me/testcase/b/b.c",
    "output": "/home/me/testcase/b/b"
  },
  {
    "arguments": [
      "/usr/bin/gcc",
      "-c",
      "-Iaa",
      "../b/b",
      "-o",
      "../test",
      "a.c"
    ],
    "directory": "/home/me/testcase/a",
    "file": "/home/me/testcase/a/a.c",
    "output": "/home/me/testcase/test"
  }
]

Check these two files with: clang-check a/a.c b/b.c
Then clang-check will complain for:

warning: ../b/b: 'linker' input unused [-Wunused-command-line-argument]
b.c:1:10: fatal error: 'A.h' file not found
#include "A.h"
         ^~~~~~~~~
1 error generated.
Error while processing testcase/b/b.c.

In which it seems failed to find the b/A.h for b/b.c.
Is this an intented behavior or just a bug? What is the correct way to use clang-check (or use libtooling) to do CTU analyze on multiple source files?

[PHIKN1GHT]

Similar issues: #37618 and #49180