Issue #21659 has been updated by nobu (Nobuyoshi Nakada). Status changed from Open to Feedback In configure.ac, we add `-Wno-missing-field-initializers` explicitly if available. Are you adding that `-Werror -Wmissing-field-initializer` by yourself? ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115014 * Author: wsfulton (William Fulton) * Status: Feedback * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/

Issue #21659 has been updated by jeremyevans0 (Jeremy Evans). wsfulton (William Fulton) wrote in #note-2:

This happens when compiling an EXTENSION. We have always used -Wmissing-field-initializers in our extensions and now they are broken. New Ruby releases really MUST NOT introduce new warnings for extensions which have to include Ruby.h.

New Ruby releases should not introduce errors in extensions. I think it is unreasonable to expect that they will not introduce warnings if you are explicitly configuring non-default warning flags. If you are combining non-default warning flags with `-Werror`, I think you are responsible for handling the issues that result from that, since it is your actions that are causing the errors. I realize this may have worked in the past for you, but that was by chance, it is not something that Ruby has officially or deliberately supported. ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115019 * Author: wsfulton (William Fulton) * Status: Feedback * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/

Issue #21659 has been updated by jeremyevans0 (Jeremy Evans). wsfulton (William Fulton) wrote in #note-4:

Fixing this warning, in particular, removes undefined behaviour.

Can you explain what the undefined behavior is? My understanding is that in both C and C++, the behavior is defined to zero-initialize all uninitialized fields. ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115032 * Author: wsfulton (William Fulton) * Status: Feedback * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/

Issue #21659 has been updated by alanwu (Alan Wu). Status changed from Feedback to Rejected `-Wmissing-field-initializers` is in `-Wextra`, not even in `-Wall`. From the [manual](https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#index-Wmissing-field...) (emphasis mine)

Warn if a structure’s initializer has some fields missing. For example, the following code causes such a warning, because x.h is __implicitly zero__:

struct s { int f, g, h; }; struct s x = { 3, 4 };

All fields are initialized, just some are done implicitly. In fact, before the patch you point to, all fields were actually uninitialized; there is strictly more initialization happening now. The warning acts more like a lint if you want to conform to a certain coding style, and isn't a flag for some material problem that ends up in the compiled artifact. It's fine to use this warning in your code, but it's unreasonable to expect ruby to use the same style as you. You can toss in a `#pragma` around `#include "ruby.h"` to fix your build. In general, `-Werror` makes your build forward incompatible with future compilers because they release with new warnings all the time. ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115039 * Author: wsfulton (William Fulton) * Status: Rejected * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/

Issue #21659 has been updated by mame (Yusuke Endoh). Fun C topic! wsfulton (William Fulton) wrote in #note-8:

A more conventional way for default aggregate initialisation is ```c++ struct RString retval = {}; ```

Unfortunately, that empty initializer is a violation of the C99 language specification. You can confirm that with `-pedantic` option: ``` $ echo 'struct { int i; } retval = {};' | gcc -pedantic -std=c99 -xc - <stdin>:1:28: warning: ISO C forbids empty initializer braces before C23 [-Wpedantic] ``` The current code isn't unnecessarily complicated for no reason. ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115070 * Author: wsfulton (William Fulton) * Status: Rejected * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/

Issue #21659 has been updated by mame (Yusuke Endoh). wsfulton (William Fulton) wrote in #note-10:

Any issues with this approach?

With that definition, you'd get a syntax error in C++ if you tried to explicitly initialize it like `struct RString retval = {RBASIC_INIT, 0};`. ---------------------------------------- Bug #21659: rstring.h error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] starting in ruby-3.3.10 https://bugs.ruby-lang.org/issues/21659#change-115165 * Author: wsfulton (William Fulton) * Status: Rejected * ruby -v: ruby 3.3.10 (2025-10-23 revision 343ea05002) [x86_64-linux] * Backport: 3.2: UNKNOWN, 3.3: UNKNOWN, 3.4: UNKNOWN ---------------------------------------- All extensions now have this error when using -Werror -Wmissing-field-initializers: ``` In file included from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic/char.h:29, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/arithmetic.h:24, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/ruby.h:28, from /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby.h:38, from example_wrap.c:1008: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h: In function ‘rbimpl_rstring_getmem’: /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:398:16: error: missing initializer for field ‘len’ of ‘struct RString’ [-Werror=missing-field-initializers] 398 | struct RString retval = {RBASIC_INIT}; | ^~~~~~~ /home/runner/.rvm/rubies/ruby-3.3.10/include/ruby-3.3.0/ruby/internal/core/rstring.h:206:10: note: ‘len’ declared here 206 | long len; | ^~~ ``` Can you please test with warnings turned on as this now breaks all extensions that rely on Ruby.h being warning free. Looks like it is due to commit https://github.com/ruby/ruby/commit/5a8d7642168f4ea0d9331fded3033c225bbc36c5 and expect that ```c++ struct RString retval = {RBASIC_INIT}; ``` should have been changed to: ```c++ struct RString retval = {RBASIC_INIT, 0}; ``` in rstring.h as well as all in the actual Ruby code base. -- https://bugs.ruby-lang.org/