I already posted this mail in comp.sys.hp and comp.sys.hp.hpu x but had
no response. As this problem might be present on other OSes than HP-UX
10.20, I crosspost it here, in the hope of getting an answer.

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In C/C++ system include files on HP-UX 10.20,
/usr/include/values.h defines macro MAXINT as (~HIBITI)
/usr/include/sys/param.h defines macro MAXINT as 0x7fffffff
...