[llvm-bugs] [Bug 38270] New: Rewriter crashes when compilation database contains files with same name

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=38270

            Bug ID: 38270
           Summary: Rewriter crashes when compilation database contains
                    files with same name
           Product: clang
           Version: 6.0
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: hyunsu.lim01 at gmail.com
                CC: llvm-bugs at lists.llvm.org

Created attachment 20586
  --> https://bugs.llvm.org/attachment.cgi?id=20586&action=edit
Example build system and program that I created to reproduce the bug

# Overview

If the compilation database contains the files with same name but different
path and size, the program written using clang libtooling and clang Rewriter
crashes.


# Steps to Reproduce

1) Create the build system that generates the following
`compile_commands.json`:
```json
[
    {
        "arguments": [
            "cc",
            "-c",
            "-o",
            "a.o",
            "a.c"
        ],
        "directory": "/home/user/build_system/lib",
        "file": "a.c"
    },
    {
        "arguments": [
            "cc",
            "-c",
            "-o",
            "a.o",
            "a.c"
        ],
        "directory": "/home/user/build_system/src",
        "file": "a.c"
    }
]
```
In here, the length of the content of `/home/user/build_system/src/a.c`
**should be larger** than that of `/home/user/build_system/lib/a.c`.

The example build system I created is attached for reference. For detailed
description about the attachment, check # About Attachment section

2) Create a program with clang libtooling, which reads the compilation database
and for every file in compilation database, does rewriting on every statement
in the file.

The example program I created is attached for reference. For detailed
description about the attachment, check # About Attachment section

3) Run the program on the created compilation database. The program runs
cleanly on `lib/a.c`, but it shows segfault when processing `src/a.c`.


# Actual Results

The program with clang libtooling shows segfault.


# Expected Results

The program with clang libtooling should run cleanly, not showing segfault.


# Tested Environment

 - OS: Ubuntu LTS 16.04 Xenial
 - LLVM Version: 6.0.1


# About Attachment

This section describes the details of attachment.

- `build_example/`: Example build system
  - `lib/`
    - `a.c`: Example c file (shorter one)
    - `Makefile`: A makefile to compile `a.c`
  - `src/`
    - `a.c`: Example c file (longer one)
    - `Makefile`: A makefile to compile `a.c`
  - `compile_commands.json`: Compilation database. This file is generated by
running the command `$ bear make`
  - `Makefile`: A makefile to build the whole example build system
- `Makefile`: A makefile to build `target.cpp`
- `target.cpp`: A program that uses clang libtooling and clang Rewriter. This
program fails when run on the given compilation database, which shouldn't


# Other Comments

I also used `clang-check` on `lib/a.c` and `src/a.c` (`$ clang-check lib/a.c
src/a.c`), and it shows errors with `src/a.c` which are not actual errors.

I think when the SourceManager processes `src/a.c`, it uses the buffer that is
created when processing `lib/a.c` (because it has same file name), and this
causes an error.

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