Hi, everyone, I've performer further research on the problem described in the "Failing C Header Checks" thread and have found something in Autoconf's behavior that I don't understand. I chalk this up to my misunderstaning of macro languages, Autoconf, or both. If I define a macro, let's say, "SCOTT", like so: AC_DEFUN([SCOTT],[ echo "In macro SCOTT" ... ]) Then I put in 'configure.in' (old build environment is using the old file name): echo "Calling SCOTT" SCOTT echo "Returned from SCOTT" How is it possible that all of the following sequence--that I am observing in my build environment--is ocurring? I don't understand how this setup works that additional code is inserted and executed between the macro call and the execution of the first line in its body. Would someone set me straight? <quote> Calling SCOTT checking for style of include used by make... GNU checking how to run the C preprocessor... /usr/intel/pkgs/gcc/2.95.3/bin/gcc -E checking for egrep... grep -E checking for non-GNU ld... /usr/bin/ld checking if the linker (/usr/bin/ld) is GNU ld... yes checking for /usr/bin/ld option to reload object files... -r checking for BSD-compatible nm... /usr/bin/nm -B checking for a sed that does not truncate output... ./configure: -g: command not found /usr/intel/bin/gsed checking whether ln -s works... yes checking how to recognise dependent libraries... pass_all checking command to parse /usr/bin/nm -B output... failed checking for ANSI C header files... no checking for sys/types.h... no checking for sys/stat.h... no checking for stdlib.h... no checking for string.h... no checking for memory.h... no [... many more checks deleted ...] In macro SCOTT ... </quote> Thanks, Scott