Sergey Poznyakoff wrote:
> With recent gnulib (v0.1-4336-gbdae9a5), attempting to compile
> parse-datetime.c fails with:
>
> $ make -k parse-datetime.o V=1
> gcc -DHAVE_CONFIG_H -I. -I.. -Wall -ggdb -MT parse-datetime.o -MD -MP -MF
> .deps/parse-datetime.Tpo -c -o parse-datetime.o parse-datetime.c
> In file included from parse-datetime.y:39:0:
> parse-datetime.y: In function 'to_tm_year':
> intprops.h:578:17: warning: integer overflow in expression [-Woverflow]
> || (tmax) + (b) < (a)))
> ^
> intprops.h:524:4: note: in expansion of macro
> '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
> (overflow (a, b, tmin, tmax) \
> ^
> intprops.h:491:10: note: in expansion of macro '_GL_INT_OP_CALC'
> ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
> ^
> intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
> _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
> ^
> parse-datetime.y:1274:9: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
> : INT_SUBTRACT_WRAPV (year, TM_YEAR_BASE, tm_year))
> ^
> parse-datetime.y: In function 'yylex':
> intprops.h:578:17: warning: integer overflow in expression [-Woverflow]
> || (tmax) + (b) < (a)))
> ^
> intprops.h:524:4: note: in expansion of macro
> '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
> (overflow (a, b, tmin, tmax) \
> ^
> intprops.h:500:11: note: in expansion of macro '_GL_INT_OP_CALC'
> ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
> ^
> intprops.h:495:7: note: in expansion of macro '_GL_INT_OP_WRAPV_LONGISH'
> : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
> ^
> intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
> _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
> ^
> parse-datetime.y:1469:23: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
> if (INT_SUBTRACT_WRAPV (s, 1, &s))
> ^
The compilation doesn't fail; it merely shows warning.
When I modify intprops.h to behave the same for all GCC versions as for GCC 5.x,
I see:
* The warning is there for all GCC versions < 10, but is fixed in GCC 10.2.0.
* GCC 9.3.0 has more details:
In file included from parse-datetime.y:39:
parse-datetime.y: In function 'to_tm_year':
intprops.h:576:17: warning: integer overflow in expression of type 'int'
results in '-2147481749' [-Woverflow]
576 | || (tmax) + (b) < (a)))
| ^
intprops.h:522:4: note: in expansion of macro '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
522 | (overflow (a, b, tmin, tmax) \
| ^~~~~~~~
intprops.h:489:10: note: in expansion of macro '_GL_INT_OP_CALC'
489 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned int, \
| ^~~~~~~~~~~~~~~
intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
389 | _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
| ^~~~~~~~~~~~~~~~
parse-datetime.y:1274:9: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
1274 | : INT_SUBTRACT_WRAPV (year, TM_YEAR_BASE, tm_year))
| ^~~~~~~~~~~~~~~~~~
parse-datetime.y: In function 'yylex':
intprops.h:576:17: warning: integer overflow in expression of type 'long int'
results in '-9223372036854775808' [-Woverflow]
576 | || (tmax) + (b) < (a)))
| ^
intprops.h:522:4: note: in expansion of macro '_GL_INT_SUBTRACT_RANGE_OVERFLOW'
522 | (overflow (a, b, tmin, tmax) \
| ^~~~~~~~
intprops.h:498:11: note: in expansion of macro '_GL_INT_OP_CALC'
498 | ? _GL_INT_OP_CALC (a, b, r, op, overflow, unsigned long int, \
| ^~~~~~~~~~~~~~~
intprops.h:493:7: note: in expansion of macro '_GL_INT_OP_WRAPV_LONGISH'
493 | : _GL_INT_OP_WRAPV_LONGISH(a, b, r, op, overflow))
| ^~~~~~~~~~~~~~~~~~~~~~~~
intprops.h:389:4: note: in expansion of macro '_GL_INT_OP_WRAPV'
389 | _GL_INT_OP_WRAPV (a, b, r, -, _GL_INT_SUBTRACT_RANGE_OVERFLOW)
| ^~~~~~~~~~~~~~~~
parse-datetime.y:1469:23: note: in expansion of macro 'INT_SUBTRACT_WRAPV'
1469 | if (INT_SUBTRACT_WRAPV (s, 1, &s))
| ^~~~~~~~~~~~~~~~~~
So, the problem is a signed-integer overflow of constants in a dead
(unreachable) code branch.
Bruno
