From: xtkoba+ruby@... Date: 2021-04-07T12:40:12+00:00 Subject: [ruby-core:103268] [Ruby master Feature#17752] Enable -Wundef for C extensions in repository Issue #17752 has been updated by xtkoba (Tee KOBAYASHI). I noticed that `-Wundef` is explicitly disabled for GCC at [include/ruby/internal/token_paste.h:40](https://github.com/ruby/ruby/blob/587e6800086764a1b7c959976acef33e230dccc2/include/ruby/internal/token_paste.h#L40): ```c #if RBIMPL_COMPILER_SINCE(GCC, 4, 2, 0) # /* GCC is one of such compiler who cannot write `_Pragma` inside of a `#if`. # * Cannot but globally kill everything. This is of course a very bad thing. # * If you know how to reroute this please tell us. */ # /* https://gcc.godbolt.org/z/K2xr7X */ # define RBIMPL_TOKEN_PASTE(x, y) TOKEN_PASTE(x, y) # pragma GCC diagnostic ignored "-Wundef" # /* > warning: "symbol" is not defined, evaluates to 0 [-Wundef] */ ``` The problem is that GCC is a major compiler that is widely used in CI, and so we will still be missing a lot of potential problems even if `-Wundef` is enabled by default. ---------------------------------------- Feature #17752: Enable -Wundef for C extensions in repository https://bugs.ruby-lang.org/issues/17752#change-91353 * Author: Eregon (Benoit Daloze) * Status: Open * Priority: Normal ---------------------------------------- I would like to enable `-Wundef` for C extensions built/bundled with CRuby. From https://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html > -Wundef > Warn if an undefined identifier is evaluated in an #if directive. Such identifiers are replaced with zero. I found this warning to be quite useful, notably when investigating why a given C extension did not include some code I expected, and then building those extensions on TruffleRuby. There are a couple places not respecting this currently but they seem trivial to fix, I can do that. For instance a confusing case is: https://github.com/ruby/ruby/blob/9143d21b1bf2f16b1e847d569a588510726d8860/ext/nkf/nkf-utf8/nkf.h#L19 ``` #if DEFAULT_NEWLINE == 0x0D0A ``` which without -Wundef would just exclude the code without any warning if DEFAULT_NEWLINE is not defined. I'm not sure if we should/can enable it for C extensions in general (installed as gems), as if a C extensions uses -Werror and would have such a warning it would no longer build. I can make a PR for this. I'm not sure where to add -Wundef though, should it be in https://github.com/ruby/ruby/blob/9143d21b1bf2f16b1e847d569a588510726d8860/configure.ac#L620, or maybe in mkmf.rb? ---Files-------------------------------- ruby-USE_BACKTRACE.patch (1.21 KB) ruby-BIGNUM_EMBED_LEN_MAX.patch (950 Bytes) ruby-COROUTINE_LIMITED_ADDRESS_SPACE.patch (711 Bytes) ruby-trivial-undefined-macros.patch (4.35 KB) -- https://bugs.ruby-lang.org/ Unsubscribe: