Hi,

At Fri, 5 Aug 2011 08:26:59 +0900,
Eric Wong wrote in [ruby-core:38802]:
> I've bisected r32833 to breaking many of my external C extension builds:
>
> $ ruby -rmkmf -e 'p have_func("rb_str_set_len")'
> checking for rb_str_set_len()... no
> false

$ ruby -v -rmkmf -e 'p have_func("rb_str_set_len")'
ruby 1.9.4dev (2011-08-05 trunk 32854) [x86_64-linux]
checking for rb_str_set_len()... yes
true

Can't you show mkmf.log file?

-- 
Nobu Nakada