We are experiencing core dumps from GNU make on Solaris 10u6 X64/X86 build systems.

It is not clear what the issue is. It is suspected to be some kind of kernel problem that has come back from 10u3 days, that went away when we went to 10u6. So it's possible it is a kernel regression but we have no evidence to point at just yet.

One of the core files when run through dbx says this:

[1] 0x0(0x0, 0x0, 0x8046574), at 0x0
 [2] waitpid(0x0, 0x0, 0x0, 0x805e942, 0x0, 0x0), at 0xfec5e2f0
 [3] reap_children(block = 0, err = 0), at 0x805ea65
 [4] new_job(file = 0x82e2ae8), at 0x805ee6d
 [5] update_file(file = 0x82e2ae8, depth = 4U), at 0x806836d
 [6] check_dep(file = (nil), depth = 4U, this_mtime = 1ULL, must_make_ptr = 0x8045354), at 0x80673e1
 [7] update_file(file = 0x8330c50, depth = 2U), at 0x8067989
 [8] check_dep(file = (nil), depth = 2U, this_mtime = 1ULL, must_make_ptr = 0x8045404), at 0x80673e1
 [9] update_file(file = 0x808c4c8, depth = 0), at 0x8067989
 [10] update_goal_chain(goals = 0x81bc2c8), at 0x80687e0
 [11] main(argc = 8, argv = 0x8046550, envp = 0x8046574), at 0x8061463

but refuses to list all the threads like it wasn't an MT process???

The core file is kind of small, 8MB or so.

This looks somewhat familiar to the issue we ran into years ago in 10u3, only on Solaris x86/x64, never on sparc.

Can't use gmake on Solaris 10u6 because it is 3.80