Bug #11962: Ruby 2.3.0 causing compile failure on extensions using a C++ compiler

• Status: Closed
• Assignee: nobu (Nobuyoshi Nakada)
• Target version: -
• ruby -v: 2.3.0
• Backport: 2.1: DONTNEED, 2.2: DONE, 2.3: DONE

[v0dro (Sameer Deshmukh)]

Hello,

I'm a contributor with the SciRuby foundation, and we have a gem called nmatrix, which is a ruby gem for linear algebra processing in Ruby.

For representing different types of data, nmatrix makes heavy use of C++ templates, which requires compilation with g++. Currently we wrap the code that defines ruby functions at C level in an extern "C" {} block in a .cpp file and use g++ to compile the file as a whole.

Upgrading to ruby 2.3.0 has caused a problem because of this change implemented in the internals of the ruby C API.

As specified in the GCC docs (https://gcc.gnu.org/onlinedocs/gcc/Other-Builtins.html) the function "__builtin_choose_expr" (that has been introduced in the latest Ruby C API) is available only for C. Thus the change is rendering our C++ extensions useless.

You can see the compile error being caused in nmatrix here: https://github.com/SciRuby/nmatrix/issues/429

I have come up with a temporary fix for this, but its only patch work and will need to be done by every single extension employing a C++ compiler.

Looking forward to a positive response from you.

[hsbt (Hiroshi SHIBATA)]

• Assignee set to nobu (Nobuyoshi Nakada)

[mrkn (Kenta Murata)]

Can I fix it by the following change?

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 7aabf5b..72523c6 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -874,7 +874,7 @@ struct RBasic {
 VALUE rb_obj_hide(VALUE obj);
 VALUE rb_obj_reveal(VALUE obj, VALUE klass); /* do not use this API to change klass information */

-#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P)
+#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P) && !defined(__cplusplus)
 # define RB_OBJ_WB_UNPROTECT_FOR(type, obj) \
     __extension__( \
        __builtin_choose_expr( \

[mrkn (Kenta Murata)]

I found the other place to be fixed.
The following patch is the complete version.

diff --git a/include/ruby/ruby.h b/include/ruby/ruby.h
index 7aabf5b..a2f42c8 100644
--- a/include/ruby/ruby.h
+++ b/include/ruby/ruby.h
@@ -620,7 +620,7 @@ int ruby_safe_level_2_warning(void) __attribute__((warning("$SAFE=2 to 4 are obs
 # ifdef RUBY_EXPORT
 #   define ruby_safe_level_2_warning() ruby_safe_level_2_error()
 # endif
-#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P)
+#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P) && !defined(__cplusplus)
 # define RUBY_SAFE_LEVEL_INVALID_P(level) \
     __extension__(\
        __builtin_choose_expr(\
@@ -874,7 +874,7 @@ struct RBasic {
 VALUE rb_obj_hide(VALUE obj);
 VALUE rb_obj_reveal(VALUE obj, VALUE klass); /* do not use this API to change klass information */

-#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P)
+#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P) && !defined(__cplusplus)
 # define RB_OBJ_WB_UNPROTECT_FOR(type, obj) \
     __extension__( \
        __builtin_choose_expr( \
@@ -1376,7 +1376,7 @@ rb_data_object_wrap_warning(VALUE klass, void *ptr, RUBY_DATA_FUNC mark, RUBY_DA
     return rb_data_object_wrap(klass, ptr, mark, free);
 }

-#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P)
+#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P) && !defined(__cplusplus)
 #define rb_data_object_wrap_warning(klass, ptr, mark, free) \
     __extension__( \
        __builtin_choose_expr( \
diff --git a/include/ruby/st.h b/include/ruby/st.h
index 190bad2..97c08b1 100644
--- a/include/ruby/st.h
+++ b/include/ruby/st.h
@@ -59,7 +59,7 @@ struct st_hash_type {

 #define ST_INDEX_BITS (sizeof(st_index_t) * CHAR_BIT)

-#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR) && defined(HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P)
+#if defined(HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR) && defined(HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P) && !defined(__cplusplus)
 # define ST_DATA_COMPATIBLE_P(type) \
    __builtin_choose_expr(__builtin_types_compatible_p(type, st_data_t), 1, 0)
 #else

[mrkn (Kenta Murata)]

• Status changed from Open to Closed

Applied in changeset r53455.

---

• ruby.h: undef HAVE_BUILTIN___BUILTIN_CHOOSE_EXPR_CONSTANT_P
  and HAVE_BUILTIN___BUILTIN_TYPES_COMPATIBLE_P on C++.
  [ruby-core:72736] [Bug #11962]

[vo.x (Vit Ondruch)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: UNKNOWN to 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: REQUIRED

[vo.x (Vit Ondruch)]

BTW this causes issues compiling SWIG:

https://github.com/swig/swig/issues/593

[terceiro (Antonio Terceiro)]

We are trying to transition Debian unstable to ruby2.3, it would be very helpful to have this applied to the 2.3 branch.

[usa (Usaku NAKAMURA)]

• Backport changed from 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN, 2.3: REQUIRED to 2.1: DONTNEED, 2.2: REQUIRED, 2.3: REQUIRED

[nagachika (Tomoyuki Chikanaga)]

• Backport changed from 2.1: DONTNEED, 2.2: REQUIRED, 2.3: REQUIRED to 2.1: DONTNEED, 2.2: DONE, 2.3: REQUIRED

Backported into ruby_2_2 branch at r54315.

[naruse (Yui NARUSE)]

• Backport changed from 2.1: DONTNEED, 2.2: DONE, 2.3: REQUIRED to 2.1: DONTNEED, 2.2: DONE, 2.3: DONE

ruby_2_3 r54364 merged revision(s) 53455.