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Express abs(z) in a way that satisfies GCC and MSVC

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Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2022-11-15 23:25:27 +01:00
parent af601f9751
commit ef7f4e47b1
1 changed files with 16 additions and 5 deletions
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21
library/bignum.c
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@ -252,6 +252,17 @@ void mbedtls_mpi_swap( mbedtls_mpi *X, mbedtls_mpi *Y )
memcpy( Y, &T, sizeof( mbedtls_mpi ) ); memcpy( Y, &T, sizeof( mbedtls_mpi ) );
} }
static inline mbedtls_mpi_uint mpi_sint_abs( mbedtls_mpi_sint z )
{
if( z >= 0 )
return( z );
/* Take care to handle the most negative value (-2^(biL-1)) correctly.
* A naive -z would have undefined behavior.
* Write this in a way that makes popular compilers happy (GCC, Clang,
* MSVC). */
return( (mbedtls_mpi_uint) 0 - (mbedtls_mpi_uint) z );
}
/* /*
* Set value from integer * Set value from integer
*/ */
@ -263,7 +274,7 @@ int mbedtls_mpi_lset( mbedtls_mpi *X, mbedtls_mpi_sint z )
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, 1 ) ); MBEDTLS_MPI_CHK( mbedtls_mpi_grow( X, 1 ) );
memset( X->p, 0, X->n * ciL ); memset( X->p, 0, X->n * ciL );
X->p[0] = ( z < 0 ) ? -(mbedtls_mpi_uint)z : z; X->p[0] = mpi_sint_abs( z );
X->s = ( z < 0 ) ? -1 : 1; X->s = ( z < 0 ) ? -1 : 1;
cleanup: cleanup:
@ -853,7 +864,7 @@ int mbedtls_mpi_cmp_int( const mbedtls_mpi *X, mbedtls_mpi_sint z )
mbedtls_mpi_uint p[1]; mbedtls_mpi_uint p[1];
MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( X != NULL );
*p = ( z < 0 ) ? -(mbedtls_mpi_uint)z : z; *p = mpi_sint_abs( z );
Y.s = ( z < 0 ) ? -1 : 1; Y.s = ( z < 0 ) ? -1 : 1;
Y.n = 1; Y.n = 1;
Y.p = p; Y.p = p;
@ -1057,7 +1068,7 @@ int mbedtls_mpi_add_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( X != NULL );
MPI_VALIDATE_RET( A != NULL ); MPI_VALIDATE_RET( A != NULL );
p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; p[0] = mpi_sint_abs( b );
B.s = ( b < 0 ) ? -1 : 1; B.s = ( b < 0 ) ? -1 : 1;
B.n = 1; B.n = 1;
B.p = p; B.p = p;
@ -1075,7 +1086,7 @@ int mbedtls_mpi_sub_int( mbedtls_mpi *X, const mbedtls_mpi *A, mbedtls_mpi_sint
MPI_VALIDATE_RET( X != NULL ); MPI_VALIDATE_RET( X != NULL );
MPI_VALIDATE_RET( A != NULL ); MPI_VALIDATE_RET( A != NULL );
p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; p[0] = mpi_sint_abs( b );
B.s = ( b < 0 ) ? -1 : 1; B.s = ( b < 0 ) ? -1 : 1;
B.n = 1; B.n = 1;
B.p = p; B.p = p;
@ -1413,7 +1424,7 @@ int mbedtls_mpi_div_int( mbedtls_mpi *Q, mbedtls_mpi *R,
mbedtls_mpi_uint p[1]; mbedtls_mpi_uint p[1];
MPI_VALIDATE_RET( A != NULL ); MPI_VALIDATE_RET( A != NULL );
p[0] = ( b < 0 ) ? -(mbedtls_mpi_uint)b : b; p[0] = mpi_sint_abs( b );
B.s = ( b < 0 ) ? -1 : 1; B.s = ( b < 0 ) ? -1 : 1;
B.n = 1; B.n = 1;
B.p = p; B.p = p;