On AIX 6.1 using IBM's XLC compiler, I do "configure" and that successfully completes. However, when I "make", it fails due to the parameters "-fstack-protector" and "-fPIE"... apparently it couldn't find the files "stack-protector" and "PIE" as "-f" specifies a file. However, gcc and perhaps many other cc variants, "-f" specifies a compile option. I was able to compile with XLC by ripping out the "stack-protector" and "PIE" sections of "configure" and running "make" but it would be best to use the stack protector mechanisms used for AIX's XLC:

https://www.ibm.com/developerworks/mydeveloperworks/blogs/b10932b4-0edd-4e61-89f2-6e478ccba9aa/entry/security_stack_protection_in_xl_compilers17?lang=en

Has anyone compiled Stunnel 5.26 using IBM's XLC without removing the stack-protector and PIE sections in the configure file?

The other option is to use gxlc instead of xlc to map the GNU C compiler options to XLC options. Would that be preferred (less modification of configure file)? I was able to get that working, but still an unusually high number of warnings.
http://geco.mines.edu/files/manuals/xlc/mapping.pdf

The article above (from IBM) has "-qstackprotect=size=N" - what suggestion parameter to use for "N"?

To be nice to everyone's mailbox, I have posted the logs here:
Stunnel 5.26 AIX XLC - fails
http://pastebin.ca/3250237

Stunnel 5.26 AIX GXLC - passes
http://pastebin.ca/3250242

Thanks,
 -Rob