Compiler: Sun Studio 10 (cc)
On Solaris (and possibly HP/UX, but I don't currently have access to an HP machine), the file asn1-func.c needs to include the alloca.h header file.
How To Repeat
Compile libksba on Solaris.
Test for Solaris (and maybe HP/UX) during configure, #ifdef/#include alloca.h is neccessary.