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1ed20a01c9
For integer promotion with for example arithmetics or
expr_cond (x ? y : z), integral types need to be promoted
to signed if they fit.
According to latest standards, this also applies to bit-field
types taking into account their specific width.
In tcc, VT_BITFIELD set means width < original type width
Field-widths between 33 and 63 are promoted to signed long long
accordingly.
struct { unsigned long long ullb:35; } s = { 1 };
#define X (s.ullb - 2)
int main (void)
{
long long Y = X;
printf("%d %016llx %016llx\n", X < 0, -X, -Y);
return 0;
}
Results:
GCC 4.7 : 0 0000000000000001 FFFFFFF800000001
MSVC : 1 0000000000000001 0000000000000001
TCC : 1 0000000000000001 0000000000000001
Also, gcc would promote long long bitfields of size < 32
to int as well. Example:
struct { unsigned long long x:20; } t = { 123 };
/* with gcc: */ printf("%d %d\n", t.x, 456);
/* with tcc: */ printf("%lld %d\n", t.x, 456);
72 lines
1.3 KiB
C
72 lines
1.3 KiB
C
/* integer promotion */
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int printf(const char*, ...);
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#define promote(s) printf(" %ssigned : %s\n", (s) - 100 < 0 ? " " : "un", #s);
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int main (void)
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{
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struct {
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unsigned ub:3;
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unsigned u:32;
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unsigned long long ullb:35;
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unsigned long long ull:64;
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unsigned char c;
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} s = { 1, 1, 1 };
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promote(s.ub);
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promote(s.u);
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promote(s.ullb);
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promote(s.ull);
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promote(s.c);
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printf("\n");
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promote((1 ? s.ub : 1));
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promote((1 ? s.u : 1));
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promote((1 ? s.ullb : 1));
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promote((1 ? s.ull : 1));
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promote((1 ? s.c : 1));
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printf("\n");
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promote(s.ub << 1);
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promote(s.u << 1);
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promote(s.ullb << 1);
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promote(s.ull << 1);
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promote(s.c << 1);
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printf("\n");
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promote(+s.ub);
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promote(+s.u);
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promote(+s.ullb);
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promote(+s.ull);
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promote(+s.c);
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printf("\n");
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promote(-s.ub);
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promote(-s.u);
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promote(-s.ullb);
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promote(-s.ull);
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promote(-s.c);
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printf("\n");
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promote(~s.ub);
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promote(~s.u);
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promote(~s.ullb);
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promote(~s.ull);
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promote(~s.c);
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printf("\n");
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promote(!s.ub);
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promote(!s.u);
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promote(!s.ullb);
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promote(!s.ull);
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promote(!s.c);
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printf("\n");
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promote(+(unsigned)s.ub);
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promote(-(unsigned)s.ub);
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promote(~(unsigned)s.ub);
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promote(!(unsigned)s.ub);
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return 0;
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}
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