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Use builtins for overflow detection in OverflowSafeInt on gcc/clang

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This commit is contained in:
Jonathan G Rennison
2020-04-20 21:48:04 +01:00
parent be3f03358f
commit 6821c0e945
2 changed files with 47 additions and 1 deletions
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23
config.lib
View File

@@ -1914,6 +1914,29 @@ EOL
CFLAGS="$CFLAGS -DWITH_BITMATH_BUILTINS"
fi
log 2 "executing $cc_host $CFLAGS $LDFLAGS $STATIC_FLAGS -o tmp.config.overflow-builtins -x c++ -"
"$cc_host" $CFLAGS $LDFLAGS $STATIC_FLAGS -o tmp.config.overflow-builtins -x c++ - 2> /dev/null << EOL
#include <cstdint>
int main() {
int64_t a = 0;
int64_t b = 0;
int64_t c = 0;
bool res1 = __builtin_add_overflow(a, b, &c);
bool res2 = __builtin_sub_overflow(a, b, &c);
bool res3 = __builtin_mul_overflow(a, b, &c);
return (res1 || res2 || res3) ? 1 : 0;
}
EOL
ret=$?
rm -f tmp.config.overflow-builtins
log 2 " exit code $ret"
if [ $ret -ne 0 ]; then
log 1 "checking overflow builtins... no"
else
log 1 "checking overflow builtins... found"
CFLAGS="$CFLAGS -DWITH_OVERFLOW_BUILTINS"
fi
if [ "$os" != "CYGWIN" ] && [ "$os" != "HAIKU" ] && [ "$os" != "MORPHOS" ] && [ "$os" != "OSX" ] && [ "$os" != "DOS" ] && [ "$os" != "WINCE" ] && [ "$os" != "PSP" ] && [ "$os" != "OS2" ]; then
log 2 "executing $cc_host $CFLAGS $CFLAGS_ENV $LDFLAGS $LDFLAGS_ENV -o tmp.config.demangle -x c++ - -lstdc++"
"$cc_host" $CFLAGS $CFLAGS_ENV $LDFLAGS $LDFLAGS_ENV -o tmp.config.demangle -x c++ - -lstdc++ 2> /dev/null << EOL

25
src/core/overflowsafe_type.hpp
View File

@@ -46,12 +46,30 @@ public:
*/
inline OverflowSafeInt& operator += (const OverflowSafeInt& other)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_add_overflow(this->m_value, other.m_value, &this->m_value))) {
this->m_value = (other.m_value < 0) ? T_MIN : T_MAX;
}
#else
if ((T_MAX - abs(other.m_value)) < abs(this->m_value) &&
(this->m_value < 0) == (other.m_value < 0)) {
this->m_value = (this->m_value < 0) ? T_MIN : T_MAX ;
} else {
this->m_value += other.m_value;
}
#endif
return *this;
}
inline OverflowSafeInt& operator -= (const OverflowSafeInt& other)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_sub_overflow(this->m_value, other.m_value, &this->m_value))) {
this->m_value = (other.m_value < 0) ? T_MAX : T_MIN;
}
#else
*this += (-other);
#endif
return *this;
}
@@ -59,7 +77,6 @@ public:
inline OverflowSafeInt operator + (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result += other; return result; }
inline OverflowSafeInt operator + (const int other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }
inline OverflowSafeInt operator + (const uint other) const { OverflowSafeInt result = *this; result += (int64)other; return result; }
inline OverflowSafeInt& operator -= (const OverflowSafeInt& other) { return *this += (-other); }
inline OverflowSafeInt operator - (const OverflowSafeInt& other) const { OverflowSafeInt result = *this; result -= other; return result; }
inline OverflowSafeInt operator - (const int other) const { OverflowSafeInt result = *this; result -= (int64)other; return result; }
inline OverflowSafeInt operator - (const uint other) const { OverflowSafeInt result = *this; result -= (int64)other; return result; }
@@ -77,11 +94,17 @@ public:
*/
inline OverflowSafeInt& operator *= (const int factor)
{
#ifdef WITH_OVERFLOW_BUILTINS
if (unlikely(__builtin_mul_overflow(this->m_value, factor, &this->m_value))) {
this->m_value = ((this->m_value < 0) == (factor < 0)) ? T_MAX : T_MIN;
}
#else
if (factor != 0 && (T_MAX / abs(factor)) < abs(this->m_value)) {
this->m_value = ((this->m_value < 0) == (factor < 0)) ? T_MAX : T_MIN ;
} else {
this->m_value *= factor ;
}
#endif
return *this;
}