AC_PROG_CC does not work correctly inside conditionals (autoconf 2.61)

[Andreas Kabel]

This problem showed up when trying to have the list of
compilers depend on some configuration variables.

It can be reproduced with the following minimal
configure.ac file:

################
AC_INIT(plibb, 0.1, address@hidden)

if false; then      # FALSE
        AC_PROG_CC
else                # ELSE
        AC_PROG_CC
fi                  # ENDIF

AC_OUTPUT
###############


Now, comparing the shell code generated for the two
branches of the conditional, e.g. by

autoconf
sed '/FALSE/,/ELSE/!d' >branch1
sed '/ELSE/,/ENDIF/!d' >branch2
diff branch1 branch2

shows that the first branch contains 252 more
lines of shell code; in particular, it contains
the code for checking the file extension of
output files. The second branch does not, resulting
in failed tests, e.g. checking for gcc being a GNU
compiler, which should succeed.

Regards,

        Andreas