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4ac91a2d81
C does not have negative integer constants so "(MR_Integer) -nnnn" is the negation of a positive integer constant nnnn, converted to MR_Integer. In C89/C90 an unsuffixed decimal integer constant must be typed `int' or `long int' or `unsigned long int', whichever fits first. The negated result will have the same type. If nnnn > LONG_MAX then it will be typed `unsigned long int'. If MR_Integer is wider than `unsigned long int' then the conversion to MR_Integer yields a positive value, not negative. The solution here is essentially to write "-(MR_Integer) nnnn" so the integer constant is converted to a signed MR_Integer before negation. After this fix we no longer get these warnings from gcc: "this decimal constant is unsigned only in ISO C90". It turns out gcc was trying to tell us something. compiler/c_util.m: Add predicate `output_int_expr' to write ints in a way that avoids the problem. compiler/llds_out_data.m: compiler/mlds_to_c.m: Use `output_int_expr' to write ints. tests/hard_coded/Mmakefile: tests/hard_coded/c89_neg_int.exp: tests/hard_coded/c89_neg_int.m: Add test case.
28 lines
671 B
Mathematica
28 lines
671 B
Mathematica
%---------------------------------------------------------------------------%
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% vim: ts=4 sw=4 et ft=mercury
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%---------------------------------------------------------------------------%
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:- module c89_neg_int.
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:- interface.
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:- import_module io.
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:- pred main(io::di, io::uo) is det.
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:- implementation.
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main(!IO) :-
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show(-2147483647, !IO),
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show(-2147483648, !IO),
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% Disabled as they will be rejected by a compiler with 32-bit ints.
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% show(-2147483649, !IO),
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% show(-9223372036854775807, !IO),
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% show(-9223372036854775808, !IO),
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true.
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:- pred show(int::in, io::di, io::uo) is det.
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show(N, !IO) :-
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io.write_int(N, !IO),
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io.nl(!IO).
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