Issue #13529 has been updated by nobu (Nobuyoshi Nakada).

Description updated
Status changed from Open to Feedback

How did you configure it?

I can't reproduce it, and `rb_cv_off_t_convertible` seems properly configured as `LONG`.

```
$ sed -i /off_t/d config.cache 

$ make reconfig | grep off_t
checking for off_t... yes
checking size of off_t... 8
checking for convertible type of off_t... LONG

$ grep off_t config.cache
ac_cv_sizeof_off_t=${ac_cv_sizeof_off_t=8}
ac_cv_type_off_t=${ac_cv_type_off_t=yes}
rb_cv_off_t_convertible=${rb_cv_off_t_convertible=LONG}

$ grep OFFT .ext/include/x86_64-cygwin/ruby/config.h 
#define OFFT2NUM(v) LONG2NUM(v)
#define NUM2OFFT(v) NUM2LONG(v)
#define PRI_OFFT_PREFIX PRI_LONG_PREFIX

$ rm io.o; make io.o
compiling ../src/io.c
```

----------------------------------------
Bug #13529: Warning when compiling io.c
https://bugs.ruby-lang.org/issues/13529#change-64609

* Author: duerst (Martin Drst)
* Status: Feedback
* Priority: Normal
* Assignee: nobu (Nobuyoshi Nakada)
* Target version: 
* ruby -v: ruby 2.5.0dev (2017-05-01 trunk 58527) [x86_64-cygwin]
* Backport: 2.2: UNKNOWN, 2.3: UNKNOWN, 2.4: UNKNOWN
----------------------------------------
I get the warning below when trying to compile trunk on cygwin:

```
compiling io.c
io.c: In function °∆do_io_advise°«:
io.c:8869:29: warning: format °∆%lld°« expects argument of type °∆long long int°«, b                              ut argument 3 has type °∆off_t {aka long int}°« [-Wformat=]
  VALUE message = rb_sprintf("%"PRIsVALUE" "




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