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Correct handling of return value of N_OP_unwind()

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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
This commit is contained in:
Nick Briggs 2021-01-01 14:08:41 -08:00
parent d717946929
commit 12c5f3231e
3 changed files with 8 additions and 6 deletions
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3
inc/inlineC.h
View File

@ -852,8 +852,7 @@ nextop2; \
#define UNWIND(n, m) \
{ \
if ((INT)(CSTKPTRL = (LispPTR *) \
N_OP_unwind(CSTKPTR, TOPOFSTACK, n, m)) < 0) \
if ((CSTKPTRL = N_OP_unwind(CSTKPTR, TOPOFSTACK, n, m)) == (LispPTR *)-1) \
goto unwind_err; \
POP; \
nextop3; \

2
inc/unwinddefs.h
View File

@ -1,4 +1,4 @@
#ifndef UNWINDDEFS_H
#define UNWINDDEFS_H 1
UNSIGNED N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int keep);
LispPTR *N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int keep);
#endif

9
src/unwind.c
View File

@ -28,7 +28,7 @@
#include "unwinddefs.h"
UNSIGNED N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int keep) {
LispPTR *N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int keep) {
register int num; /* number of UNBOUND slot */
register LispPTR *endptr; /* unwind limit */
register LispPTR *lastpvar; /* points PVar slot that is unbounded. */
@ -64,7 +64,10 @@ UNSIGNED N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int
if (endptr > cstkptr) {
CurrentStackPTR = (DLword *)cstkptr;
ERROR_EXIT(tos);
/* this would be ERROR_EXIT(tos); but for having to return a pointer */
TopOfStack = tos;
Error_Exit = 1;
return (LispPTR *)(-1);
}
*cstkptr++ = tos;
@ -85,7 +88,7 @@ UNSIGNED N_OP_unwind(register LispPTR *cstkptr, register LispPTR tos, int n, int
/* endptr = cstkptr */
if (keep) { *(cstkptr++) = tos; }
return ((UNSIGNED)cstkptr);
return (cstkptr);
} /* N_OP_unwind */