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AC_PROG_CC fails when target C library is missing fopen

From: Adam Sampson
Subject: AC_PROG_CC fails when target C library is missing fopen
Date: Wed, 5 Aug 2009 18:56:00 +0100
User-agent: Mutt/1.5.19 (2009-01-05)


I've upgraded to autoconf 2.64 recently, and it works nicely -- except
in one slightly odd configuration.

One of the projects I work on (KRoC, an occam compiler and runtime) can
be cross-compiled for the AVR series of microcontrollers. This used to
work, but now this happens:

checking for avr-gcc... avr-gcc
checking for C compiler default output file name... 
configure: error: in `/home/ats/src/kroc-svn/obj-avr/modules/inmoslibs/libsrc':
configure: error: C compiler cannot create executables
See `config.log' for more details.

What's going on? Well, the AC_PROG_CC test now tries to compile a little
program that uses fopen -- but the AVR-GCC toolchain uses avr-libc,
which doesn't provide fopen. (Which might seem silly -- and is certainly
non-standards-compliant -- but kind of makes sense when your typical
target device is a microcontroller with 8K of flash, and nothing even
vaguely resembling a filesystem.) In 2.63 and earlier, the program it
compiled just did "return 0;", so it was quite happy with avr-libc.

Any suggestions? I suppose one option would be to try to persuade the
avr-libc maintainers to add a dummy fopen() implementation that always
returns NULL...


Adam Sampson <address@hidden>                         <http://offog.org/>

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