Re: cygwin -mno-cygwin AC_CHECK_SIZEOF

[Eric Blake]

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According to Keith MARSHALL on 12/1/2006 7:56 AM:
>>  checking for MAP_ANON in sys/mman.h... no
>>  checking for /dev/zero... configure: error: cannot check for file
>>  existence when cross compiling
>>
>> This comes from the
>>  AC_CHECK_FILE(/dev/zero)
> 
> That's because AC_CHECK_FILE tests a feature of the *host*, not the
> *build* environment.  If you use AC_CHECK_FILE in your configure.ac,
> (or if you insist, configure.in) then you *cannot* cross compile the
> application.  And, if you want to build MinGW apps under Cygwin, you
> *must* be able to cross compile.

One other thing you can do to try to still allow cross-compiling in this
case is to prepopulate the cache.  Since mingw doesn't have /dev/zero, you
might be able to get away with running './configure ...
ac_cv_file_dev_zero=no'.  But I also wonder why this application is
checking for /dev/zero - there are a number of unportable mmap checking
macros out there in the world, that should be improved to not even attempt
the AC_CHECK_FILE when cross-compiling.

- --
Life is short - so eat dessert first!

Eric Blake             address@hidden
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