+# PGAC_C_BUILTIN_OP_OVERFLOW
+# -------------------------
+# Check if the C compiler understands __builtin_$op_overflow(),
+# and define HAVE__BUILTIN_OP_OVERFLOW if so.
+#
+# Check for the most complicated case, 64 bit multiplication, as a
+# proxy for all of the operations.
+AC_DEFUN([PGAC_C_BUILTIN_OP_OVERFLOW],
+[AC_CACHE_CHECK(for __builtin_mul_overflow, pgac_cv__builtin_op_overflow,
+[AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],
+[PG_INT64_TYPE result;
+__builtin_mul_overflow((PG_INT64_TYPE) 1, (PG_INT64_TYPE) 2, &result);]
+)],
+[pgac_cv__builtin_op_overflow=yes],
+[pgac_cv__builtin_op_overflow=no])])
+if test x"$pgac_cv__builtin_op_overflow" = xyes ; then
+AC_DEFINE(HAVE__BUILTIN_OP_OVERFLOW, 1,
+ [Define to 1 if your compiler understands __builtin_$op_overflow.])
+fi])# PGAC_C_BUILTIN_OP_OVERFLOW
+
+
+
# PGAC_C_BUILTIN_UNREACHABLE
# --------------------------
# Check if the C compiler understands __builtin_unreachable(),
--- /dev/null
+/*-------------------------------------------------------------------------
+ *
+ * int.h
+ * Routines to perform integer math, while checking for overflows.
+ *
+ * The routines in this file are intended to be well defined C, without
+ * relying on compiler flags like -fwrapv.
+ *
+ * To reduce the overhead of these routines try to use compiler intrinsics
+ * where available. That's not that important for the 16, 32 bit cases, but
+ * the 64 bit cases can be considerably faster with intrinsics. In case no
+ * intrinsics are available 128 bit math is used where available.
+ *
+ * Copyright (c) 2017, PostgreSQL Global Development Group
+ *
+ * src/include/common/int.h
+ *
+ *-------------------------------------------------------------------------
+ */
+#ifndef COMMON_INT_H
+#define COMMON_INT_H
+
+/*
+ * If a + b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_add_s16_overflow(int16 a, int16 b, int16 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_add_overflow(a, b, result);
+#else
+ int32 res = (int32) a + (int32) b;
+
+ if (res > PG_INT16_MAX || res < PG_INT16_MIN)
+ return true;
+ *result = (int16) res;
+ return false;
+#endif
+}
+
+/*
+ * If a - b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_sub_s16_overflow(int16 a, int16 b, int16 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_sub_overflow(a, b, result);
+#else
+ int32 res = (int32) a - (int32) b;
+
+ if (res > PG_INT16_MAX || res < PG_INT16_MIN)
+ return true;
+ *result = (int16) res;
+ return false;
+#endif
+}
+
+/*
+ * If a * b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_mul_s16_overflow(int16 a, int16 b, int16 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_mul_overflow(a, b, result);
+#else
+ int32 res = (int32) a * (int32) b;
+
+ if (res > PG_INT16_MAX || res < PG_INT16_MIN)
+ return true;
+ *result = (int16) res;
+ return false;
+#endif
+}
+
+/*
+ * If a + b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_add_s32_overflow(int32 a, int32 b, int32 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_add_overflow(a, b, result);
+#else
+ int64 res = (int64) a + (int64) b;
+
+ if (res > PG_INT32_MAX || res < PG_INT32_MIN)
+ return true;
+ *result = (int32) res;
+ return false;
+#endif
+}
+
+/*
+ * If a - b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_sub_s32_overflow(int32 a, int32 b, int32 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_sub_overflow(a, b, result);
+#else
+ int64 res = (int64) a - (int64) b;
+
+ if (res > PG_INT32_MAX || res < PG_INT32_MIN)
+ return true;
+ *result = (int32) res;
+ return false;
+#endif
+}
+
+/*
+ * If a * b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_mul_s32_overflow(int32 a, int32 b, int32 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_mul_overflow(a, b, result);
+#else
+ int64 res = (int64) a * (int64) b;
+
+ if (res > PG_INT32_MAX || res < PG_INT32_MIN)
+ return true;
+ *result = (int32) res;
+ return false;
+#endif
+}
+
+/*
+ * If a + b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_add_s64_overflow(int64 a, int64 b, int64 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_add_overflow(a, b, result);
+#elif defined(HAVE_INT128)
+ int128 res = (int128) a + (int128) b;
+
+ if (res > PG_INT64_MAX || res < PG_INT64_MIN)
+ return true;
+ *result = (int64) res;
+ return false;
+#else
+ if ((a > 0 && b > 0 && a > PG_INT64_MAX - b) ||
+ (a < 0 && b < 0 && a < PG_INT64_MIN - b))
+ return true;
+ *result = a + b;
+ return false;
+#endif
+}
+
+/*
+ * If a - b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_sub_s64_overflow(int64 a, int64 b, int64 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_sub_overflow(a, b, result);
+#elif defined(HAVE_INT128)
+ int128 res = (int128) a - (int128) b;
+
+ if (res > PG_INT64_MAX || res < PG_INT64_MIN)
+ return true;
+ *result = (int64) res;
+ return false;
+#else
+ if ((a < 0 && b > 0 && a < PG_INT64_MIN + b) ||
+ (a > 0 && b < 0 && a > PG_INT64_MAX + b))
+ return true;
+ *result = a - b;
+ return false;
+#endif
+}
+
+/*
+ * If a * b overflows, return true, otherwise store the result of a + b into
+ * *result. The content of *result is implementation defined in case of
+ * overflow.
+ */
+static inline bool
+pg_mul_s64_overflow(int64 a, int64 b, int64 *result)
+{
+#if defined(HAVE__BUILTIN_OP_OVERFLOW)
+ return __builtin_mul_overflow(a, b, result);
+#elif defined(HAVE_INT128)
+ int128 res = (int128) a * (int128) b;
+
+ if (res > PG_INT64_MAX || res < PG_INT64_MIN)
+ return true;
+ *result = (int64) res;
+ return false;
+#else
+ /*
+ * Overflow can only happen if at least one value is outside the range
+ * sqrt(min)..sqrt(max) so check that first as the division can be quite a
+ * bit more expensive than the multiplication.
+ *
+ * Multiplying by 0 or 1 can't overflow of course and checking for 0
+ * separately avoids any risk of dividing by 0. Be careful about dividing
+ * INT_MIN by -1 also, note reversing the a and b to ensure we're always
+ * dividing it by a positive value.
+ *
+ */
+ if ((a > PG_INT32_MAX || a < PG_INT32_MIN ||
+ b > PG_INT32_MAX || b < PG_INT32_MIN) &&
+ a != 0 && a != 1 && b != 0 && b != 1 &&
+ ((a > 0 && b > 0 && a > PG_INT64_MAX / b) ||
+ (a > 0 && b < 0 && b < PG_INT64_MIN / a) ||
+ (a < 0 && b > 0 && a < PG_INT64_MIN / b) ||
+ (a < 0 && b < 0 && a < PG_INT64_MAX / b)))
+ {
+ return true;
+ }
+ *result = a * b;
+ return false;
+#endif
+}
+
+#endif /* COMMON_INT_H */
projects / postgresql / commitdiff