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Re: A problem with mmap on Win98

On Tue, May 06, 2003 at 04:07:49PM +0800, Steve Underwood wrote:
I am using the current version of cygwin (1.3.22). When I build gcc to cross-compile for the TI MSP430 MCUs the result works OK on 2000 and XP machines. On some Win98 and Me machines it works, but on others it crashes with a segmentation violation. I traced this to a problem with anonymous mmap. If I keep calling mmap on the problem machines it keeps returning the same memory pointer twice. If I patch GCC to check for a repeat of the same memory pointer, and allocate again until it gets a different pointer, my GCC build seems to run OK on these problem machines.

The results are not random. They follow a pattern. If I allocate 65536 byte blocks, I consistently get the same pointer twice, before I get a pointer 65536 bytes greater. If I allocate 16384 byte blocks, I get four pointers incrementing by 0x4000 each. Then I get a repeat of the fourth pointer. Then I get four more properly incrementing pointers.

Weird, especially that it only happens on 9x...

Its weird that there is trouble with windows? :-)

Its only on some Win9x machines, too. I did my original software testing and
produced a binary installer on a Win98SE machine that worked without a hitch.
Then various users started complaining it would not work for them. Now I have
found a Win98SE machine that exhibits the problem, so I can follow up on it.
Perhaps the different behaviour relates to the system patch level, or something.

I tried downloading the source code for cygwin, to build it, and do a little debugging of my own. However, the make files build most of the code, and then fail saying there is no rule to make /usr/lib/w32api/Makefile needed by /lib/. The make dependancies are a little intertwined, and I gave up trying to find the cause of this problem.

Did you build in the source dir? Don't do this. For more info see

I tries building in the suorce dir. Then I read the instructions, so I tried again using another dir. In both cases I got the same error.

Can anyone help?

Please create a *brief* testcase in C which encounters the above mmap problem and send it to this list. I'll have a look, then.

Did I mention that the testcase should be as short as possible?

Is gcc-core-3.2.3 built for C support a small enough test case? :-)

Seriously, it may be better if I debug this a little, as I have a machine
exhibiting the problem. I have no idea what proportion of Win98 machines succeed
and fail.

Does anyone have pointers to solving my cygwin build problem? I have the latest
cygwin (updated this week) installed on a WinXP machine, including (of course) the
development tools packages. I downloaded the source for the current version of the
cygwin DLL. I configured to build in another directory, and got the error message
described above.


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