From: "jeremyevans0 (Jeremy Evans)" <noreply@...>
Date: 2022-05-25T18:39:20+00:00
Subject: [ruby-core:108702] [Ruby master Bug#18785] RbConfig::MAKEFILE_CONFIG["warnflags"] contains "-Wno-cast-function-type" which is not compatible with clang 13.0.0

Issue #18785 has been updated by jeremyevans0 (Jeremy Evans).

Status changed from Open to Feedback

dorianmariefr (Dorian Mari��) wrote in #note-2:
> Should the fix be backported?

If you can bisect and find the fixing commit, we can mark it for backporting.  Whether to backport is always up to the branch maintainer.

----------------------------------------
Bug #18785: RbConfig::MAKEFILE_CONFIG["warnflags"] contains "-Wno-cast-function-type" which is not compatible with clang 13.0.0
https://bugs.ruby-lang.org/issues/18785#change-97746

* Author: dorianmariefr (Dorian Mari��)
* Status: Feedback
* Priority: Normal
* ruby -v: ruby 3.1.2p20 (2022-04-12 revision 4491bb740a) [arm64-darwin21]
* Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN
----------------------------------------
Hi,

I was having an issue installing the curses gem: https://github.com/ruby/curses/issues/41#issuecomment-1127293843

A minimal reproduction script is:

```ruby
require "mkmf"

curses = ["ncurses.h"]

convertible_int('chtype', [["#undef MOUSE_MOVED\n"]]+curses)
```

Then in the output of mkmf.log https://gist.github.com/b938f83aac977cd6db2a2e216b6ff17b

There is:

```
DYLD_FALLBACK_LIBRARY_PATH=.:/Users/dorianmariefr/.asdf/installs/ruby/3.1.2/lib "clang -I/Users/dorianmariefr/.asdf/installs/ruby/3.1.2/include/ruby-3.1.0/arm64-darwin21 -I/Users/dorianmariefr/.asdf/installs/ruby/3.1.2/include/ruby-3.1.0/ruby/backward -I/Users/dorianmariefr/.asdf/installs/ruby/3.1.2/include/ruby-3.1.0 -I. -I/Users/dorianmariefr/.asdf/installs/ruby/3.1.2/include  -D_XOPEN_SOURCE -D_DARWIN_C_SOURCE -D_DARWIN_UNLIMITED_SELECT -D_REENTRANT   -fdeclspec -O3 -fno-fast-math -ggdb3 -Wall -Wextra -Wdeprecated-declarations -Wdivision-by-zero -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wshorten-64-to-32 -Wwrite-strings -Wold-style-definition -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wunused-variable -Wextra-tokens -Wundef  -fno-common -pipe  -Werror -c conftest.c"
error: unknown warning option '-Wno-cast-function-type'; did you mean '-Wno-bad-function-cast'? [-Werror,-Wunknown-warning-option]
checked program was:
/* begin */
 1: #include "ruby.h"
 2:��
 3: #undef MOUSE_MOVED
 4:��
 5: #include <ncurses.h>
 6:��
 7: typedef chtype rbcv_typedef_;
 8:��
 9: extern rbcv_typedef_ foo();
10: extern unsigned long long foo();
/* end */

--------------------
```

In particular the -Wno-cast-function-type is not compatible with clang 13.0.0

```
clang -v
Apple clang version 13.0.0 (clang-1300.0.27.3)
Target: arm64-apple-darwin21.3.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin
```

After debugging, it seems to be coming from `RbConfig::MAKEFILE_CONFIG["warnflags"]`:

```
> RbConfig::MAKEFILE_CONFIG["warnflags"] 
=> "-Wall -Wextra -Wdeprecated-declarations -Wdivision-by-zero -Wimplicit-function-declaration -Wimplicit-int -Wmisleading-indentation -Wpointer-arith -Wshorten-64-to-32 -Wwrite-strings -Wold-style-definition -Wmissing-noreturn -Wno-cast-function-type -Wno-constant-logical-operand -Wno-long-long -Wno-missing-field-initializers -Wno-overlength-strings -Wno-parentheses-equality -Wno-self-assign -Wno-tautological-compare -Wno-unused-parameter -Wno-unused-value -Wunused-variable -Wextra-tokens -Wundef"
```

Another project had the same issue and the solution seems to be doing feature detection:

https://github.com/tarantool/tarantool/commit/a8c214c2ddf151139b7be70c95328a3a15fe29e2

```
check_c_compiler_flag("-Wno-cast-function-type" CC_HAS_WNO_CAST_FUNCTION_TYPE)

# ...

    if (CC_HAS_WNO_CAST_FUNCTION_TYPE)
        add_compile_flags("C;CXX" "-Wno-cast-function-type")
    endif()
```



-- 
https://bugs.ruby-lang.org/

Unsubscribe: <mailto:ruby-core-request@ruby-lang.org?subject=unsubscribe>
<http://lists.ruby-lang.org/cgi-bin/mailman/options/ruby-core>