--with-cflags="-Wno-error=implicit-function-declaration" 有什么作用？

Question

当我在这里遇到这个解决方案时，我正在努力将 thin 作为依赖项安装在 Ruby 项目中：https://github.com/macournoyer/thin/issues/365#issuecomment-692063842 (gem install thin -v '1.7.2' -- --with-cflags="-Wno-error=implicit-function-declaration")

它有效，但我对 Ruby 不是很熟悉，所以不知道为什么。这面旗帜在做什么？为什么它使安装工作没有任何问题？

---

在此修复之前我遇到的错误：

❯ gem install thin -v '1.7.2'                                 
Building native extensions. This could take a while...
ERROR:  Error installing thin:
        ERROR: Failed to build gem native extension.

    current directory: /Users/XXX/.gem/ruby/2.7.1/gems/thin-1.7.2/ext/thin_parser
/Users/XXX/.rubies/ruby-2.7.1/bin/ruby -I /Users/XXX/.rubies/ruby-2.7.1/lib/ruby/2.7.0 -r ./siteconf20210923-79304-z21dcg.rb extconf.rb
checking for main() in -lc... yes
creating Makefile

current directory: /Users/XXX/.gem/ruby/2.7.1/gems/thin-1.7.2/ext/thin_parser
make "DESTDIR=" clean

current directory: /Users/XXX/.gem/ruby/2.7.1/gems/thin-1.7.2/ext/thin_parser
make "DESTDIR="
compiling parser.c
parser.c:31:18: warning: unused variable 'http_parser_en_main' [-Wunused-const-variable]
static const int http_parser_en_main = 1;
                 ^
1 warning generated.
compiling thin.c
thin.c:242:3: error: implicit declaration of function 'thin_http_parser_init' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  thin_http_parser_init(hp);
  ^
thin.c:242:3: note: did you mean 'http_parser_init'?
./parser.h:41:5: note: 'http_parser_init' declared here
int http_parser_init(http_parser *parser);
    ^
thin.c:260:3: error: implicit declaration of function 'thin_http_parser_init' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  thin_http_parser_init(http);
  ^
thin.c:277:3: error: implicit declaration of function 'thin_http_parser_init' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  thin_http_parser_init(http);
  ^
thin.c:294:3: error: implicit declaration of function 'thin_http_parser_finish' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  thin_http_parser_finish(http);
  ^
thin.c:294:3: note: did you mean 'Thin_HttpParser_finish'?
thin.c:290:7: note: 'Thin_HttpParser_finish' declared here
VALUE Thin_HttpParser_finish(VALUE self)
      ^
thin.c:296:10: error: implicit declaration of function 'thin_http_parser_is_finished' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  return thin_http_parser_is_finished(http) ? Qtrue : Qfalse;
         ^
thin.c:334:5: error: implicit declaration of function 'thin_http_parser_execute' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    thin_http_parser_execute(http, dptr, dlen, from);
    ^
thin.c:334:5: note: did you mean 'Thin_HttpParser_execute'?
thin.c:317:7: note: 'Thin_HttpParser_execute' declared here
VALUE Thin_HttpParser_execute(VALUE self, VALUE req_hash, VALUE data, VALUE start)
      ^
thin.c:338:8: error: implicit declaration of function 'thin_http_parser_has_error' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
    if(thin_http_parser_has_error(http)) {
       ^
thin.c:338:8: note: did you mean 'http_parser_has_error'?
./parser.h:44:5: note: 'http_parser_has_error' declared here
int http_parser_has_error(http_parser *parser);
    ^
thin.c:359:10: error: implicit declaration of function 'thin_http_parser_has_error' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  return thin_http_parser_has_error(http) ? Qtrue : Qfalse;
         ^
thin.c:374:10: error: implicit declaration of function 'thin_http_parser_is_finished' is invalid in C99 [-Werror,-Wimplicit-function-declaration]
  return thin_http_parser_is_finished(http) ? Qtrue : Qfalse;
         ^
9 errors generated.
make: *** [thin.o] Error 1

make failed, exit code 2

Gem files will remain installed in /Users/XXX/.gem/ruby/2.7.1/gems/thin-1.7.2 for inspection.
Results logged to /Users/XXX/.gem/ruby/2.7.1/extensions/x86_64-darwin-19/2.7.0-static/thin-1.7.2/gem_make.out

Answer 1

我没有正确读取堆栈跟踪...

看起来这个标志基本上是在告诉编译器忽略函数隐式声明的位置，而不是在发生这种情况时出错。