How to troubleshoot build flags

[Richard Shaw]

Does anyone have a favorite method of figuring out what build flags are
causing an issue?

I'm trying to package WSPR[1] for the ham radio sig. It is autotools based
and when I use %configure the build fails but when I just use plain
configure it succeeds. It uses gfortran and f2py extensively which I think
is part of it.

The last command prior to the error is identical regardless of which
configure I use so I'm guessing the build flags for one of the input
objects to the gfortran linking phase is causing the issue.

Here's a snippet of the error although my question is how to troubleshoot
these types of problems in general:

/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/crt1.o: In
function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
rmbadname1: Replacing "len" with "len_bn".
/usr/lib/gcc/x86_64-redhat-linux/4.8.2/../../../../lib64/crt1.o: In
function `_start':
(.text+0x20): undefined reference to `main'
collect2: error: ld returned 1 exit status
error: Command "/usr/bin/gfortran -Wall -Wl,-z,relro -Wl,-z,relro
/tmp/tmpom3x2m/tmp/tmpom3x2m/src.linux-x86_64-3.3/wmodule.o
/tmp/tmpom3x2m/tmp/tmpom3x2m/src.linux-x86_64-3.3/fortranobject.o
/tmp/tmpom3x2m/wspr1.o /tmp/tmpom3x2m/getfile.o
/tmp/tmpom3x2m/paterminate.o /tmp/tmpom3x2m/audiodev.o
/tmp/tmpom3x2m/tmp/tmpom3x2m/src.linux-x86_64-3.3/w-f2pywrappers.o thnix.o
libwspr.a -L/usr/lib64 -lfftw3f -lgfortran -lportaudio -lpthread
-lsamplerate -lpython3.3m -lgfortran -o ./w.cpython-33m.so" failed with
exit status 1
make: *** [WsprMod/w.so] Error 1

Thanks,
Richard

[1] http://physics.princeton.edu/pulsar/K1JT/wspr.html
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