to Otheus:
gprof -l complains about missing call-graph data, which I don't quite understand, but that is beyond the point in this thread.

to Jim:

On SCO
$ truss ./tstloop
semsys(1, 2819742, 2, 0, 0, 0) = 18827
semsys(0, 18827, 2, 6, 2147483024, 0) = 0
.
.
.
repeats on and on for 5,000,000 times, as coded.
I don't see any brk here.

On Linux
$ strace -Tc ./tstloop
time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
50.85 62.145774 29 2134526 semctl
49.15 60.059067 28 2134527 semget
0.00 0.000088 18 5 old_mmap
0.00 0.000054 18 3 mprotect
0.00 0.000039 20 2 open
0.00 0.000028 14 2 fstat64
0.00 0.000025 13 2 close
0.00 0.000020 20 1 munmap
0.00 0.000018 18 1 read
0.00 0.000018 18 1 uname
0.00 0.000018 18 1 stat64
0.00 0.000014 14 1 1 access
0.00 0.000014 14 1 set_thread_area
0.00 0.000012 12 1 time
0.00 0.000008 8 1 brk
------ ----------- ----------- --------- --------- ----------------
100.00 122.205197 4269075 1 total

when I try
$ strace ./tstloop
semget(1660977153, 2, IPC_CREAT|0777) = 32769 <0.000028>
semctl(32769, 2, IPC_64|GETALL, 0xfeead064) = 0 <0.000029>
.
.
.

Does this output clarifies anything?