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Interlisp.maiko/inc/unwinddefs.h
Nick Briggs 12c5f3231e Correct handling of return value of N_OP_unwind()
The return value of N_OP_unwind is really of type LispPTR *, however it was
declared as UNSIGNED (effectively uintptr_t) so that the ERROR_EXIT macro
could be used to return an error indication (-1, =UINT_MAX). The call site
checked for the error condition with (int)result < 0, not accounting for the
case where a native pointer may have the high-order bit set.

We correct this problem by declaring the return type as LispPTR *,
and expand the ERROR_EXIT macro in place substituting (LispPTR *)(-1)
as the error return value, and at the single call site check for equality
with that same value.

The test case was executing the opcode tester on a Raspberry Pi or
a BeagleBone Black/Debian 10.3 where the non-error result was > 0xB0000000

  	modified:   inc/inlineC.h
        modified:   inc/unwinddefs.h
        modified:   src/unwind.c
2021-01-01 14:08:41 -08:00

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C

#ifndef UNWINDDEFS_H
#define UNWINDDEFS_H 1
LispPTR *N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int keep);
#endif