From: "byroot (Jean Boussier) via ruby-core" <ruby-core@...>
Date: 2026-07-07T06:04:51+00:00
Subject: [ruby-core:125945]  [Ruby Bug#22184] error: conflicting types for	‘OnigUChar’; have ‘char16_t’ {aka	‘short unsigned int’} since

Issue #22184 has been updated by byroot (Jean Boussier).

Assignee set to byroot (Jean Boussier)

Thank you for the report, I will try to find a way to embed T_REGEXP without including `onigmo.h` (no idea how at this point).



----------------------------------------
Bug #22184: error: conflicting types for ���OnigUChar���; have ���char16_t��� {aka ���short unsigned int���} since
https://bugs.ruby-lang.org/issues/22184#change-117912

* Author: yahonda (Yasuo Honda)
* Status: Open
* Assignee: byroot (Jean Boussier)
* ruby -v: ruby 4.1.0dev (2026-07-07T04:45:34Z master 86a6b79e5d) +PRISM [x86_64-linux]
* Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN
----------------------------------------
This issue was found at Rails Nightly CI https://buildkite.com/rails/rails-nightly/builds/4522#019f393b-4212-453f-8f4f-c1a538af23e5/L3911

### Steps to reproduce
1. Install these packages (this repro uses Ubuntu 26.04)
```
sudo apt-get install -y gcc make libicu-dev
```

2. Create extconf.rb and repro.c

- extconf.rb
```
require "mkmf"
create_makefile("repro")
```

- repro.c
```
#include <ruby.h>
#include <unicode/uchar.h>
```

3. Run `ruby.extconf & make`

```
ruby extconf
make
```

### Expected behavior
It should pass like:

```
$ ruby extconf.rb && make
creating Makefile
linking shared-object repro.so
```

### Actual behavior
It raises the ` error: conflicting types for ���OnigUChar���; have ���char16_t��� {aka ���short unsigned int���}`

```
$ ruby extconf.rb
creating Makefile
$ make
compiling repro.c
In file included from /home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby/internal/core/rregexp.h:30,
                 from /home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby/internal/core.h:31,
                 from /home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby/ruby.h:29,
                 from /home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby.h:38,
                 from repro.c:1:
/home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby/onigmo.h:76:16: error: conflicting types for ���OnigUChar���; have ���char16_t��� {aka ���short unsigned int���}
   76 | # define UChar OnigUChar
      |                ^~~~~~~~~
/home/yahonda/.local/share/mise/installs/ruby/trunk/include/ruby-4.1.0+4/ruby/onigmo.h:79:24: note: previous declaration of ���OnigUChar��� with type ���OnigUChar��� {aka ���unsigned char���}
   79 | typedef unsigned char  OnigUChar;
      |                        ^~~~~~~~~
make: *** [Makefile:251: repro.o] Error 1
$
```

### Workaround
Setting `CPPFLAGS=-DONIG_ESCAPE_UCHAR_COLLISION` workarounds this error.

```ruby
$ ruby -v
ruby 4.1.0dev (2026-07-07T04:45:34Z master 86a6b79e5d) +PRISM [x86_64-linux]
yahonda@myubuntu:~/src/github.com/yahonda/ruby-head-uchar-repro$ ruby extconf.rb
creating Makefile
$ make CPPFLAGS=-DONIG_ESCAPE_UCHAR_COLLISION
compiling repro.c
linking shared-object repro.so
$
```

Reference https://github.com/rails/buildkite-config/pull/187 



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