[ruby-core:41895] [ruby-trunk - Bug #5833] [mingw] trivial patch for thread.c build warning

Issue #5833 has been updated by Jon Forums.


Redmine appears to have chopped off your feedback and questions...inserting your questions and my answers.


> I think rb_fd_max() should return int. Is there any possibility that
> fdset->fd_count overflow signed int?

In real-world usage, I don't know with 100% certainty.

But since the following returns a `u_int` on Windows

https://github.com/ruby/ruby/blob/trunk/include/ruby/intern.h#L298

and this returns `FD_SETSIZE` (usually #defined)

https://github.com/ruby/ruby/blob/trunk/include/ruby/intern.h#L314

overflow of signed int _might_ be a possibility.

Why do you think `rb_fd_max` should return `int` rather than `unsigned int`? Is it because of this:

https://github.com/ruby/ruby/blob/trunk/include/ruby/intern.h#L260

Do you think there is a possibility of returning a negative int (maybe an extension?) in a *valid* real-world scenario?



> Moreover Windows fd_set::fd_count has u_int type if a documentation is
> correct (I saw http://msdn.microsoft.com/en-us/library/windows/desktop/ms737873(v=vs.85).aspx)
> and  size_t is not an alias of u_int.

For 32bit mingw64, headers appear to have `typedef unsigned int size_t` like lines 380-388 of:

http://mingw-w64.svn.sourceforge.net/viewvc/mingw-w64/tags/v2.0.1/mingw-w64-headers/crt/_mingw.h.in?revision=4710&view=markup

For 32bit mingw64, `fdset->fd_count` type is `u_int`:

http://mingw-w64.svn.sourceforge.net/viewvc/mingw-w64/tags/v2.0.1/mingw-w64-headers/include/psdk_inc/_fd_types.h?revision=4710&view=markup

with `typedef unsigned int u_int` like:

http://mingw-w64.svn.sourceforge.net/viewvc/mingw-w64/tags/v2.0.1/mingw-w64-headers/crt/_bsd_types.h?revision=4710&view=markup

And I see similar typedefs when searching my local mingw.org headers for `u_int` and `size_t`.

In my Windows 7 SDK I see the following in `io.h` and `crtdefs.h`:

  #ifndef _SIZE_T_DEFINED
  #ifdef  _WIN64
  typedef unsigned __int64    size_t;
  #else
  typedef _W64 unsigned int   size_t;
  #endif
  #define _SIZE_T_DEFINED
  #endif

in which `_W64` is defined like i:

  #if !defined(_W64)
  #if !defined(__midl) && (defined(_X86_) || defined(_M_IX86))
  #define _W64 __w64
  #else
  #define _W64
  #endif
  #endif

----------------------------------------
Bug #5833: [mingw] trivial patch for thread.c build warning
https://bugs.ruby-lang.org/issues/5833

Author: Jon Forums
Status: Open
Priority: Normal
Assignee: 
Category: core
Target version: 2.0.0
ruby -v: -


When building with MinGW (not Windows SDK) on Win7 I get the following:

compiling ../../../../Users/Jon/Documents/RubyDev/ruby-git/thread.c
../../../../Users/Jon/Documents/RubyDev/ruby-git/thread.c: In function 'rb_fd_rcopy':
../../../../Users/Jon/Documents/RubyDev/ruby-git/thread.c:2471:33: warning: comparison between signed and unsigned integer expressions [-Wsign-compare]


Below is a trivial patch that fixes the warning on MinGW. The patch successfully builds and tests with MinGW and Windows SDK on Win7 32bit. When building on Arch Linux, the patched build gives the same `make test && make test-all` results (6 errors, 45 skips) as an unpatched build. In all other uses in `thread.c` (except for `rb_fd_rcopy`) the `rb_fd_max` macro generates a `size_t` object. From what I can tell, use cases are all unsigned int's.

diff --git a/thread.c b/thread.c
index d9fe5506..0b48061 100644
--- a/thread.c
+++ b/thread.c
@@ -2463,7 +2463,7 @@ rb_fd_init_copy(rb_fdset_t *dst, rb_fdset_t *src)
 static void
 rb_fd_rcopy(fd_set *dst, rb_fdset_t *src)
 {
-    int max = rb_fd_max(src);
+    size_t max = rb_fd_max(src);
 
     /* we assume src is the result of select() with dst, so dst should be
      * larger or equal than src. */



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