diff options
Diffstat (limited to 'lib/intprops.h')
| -rw-r--r-- | lib/intprops.h | 27 |
1 files changed, 18 insertions, 9 deletions
diff --git a/lib/intprops.h b/lib/intprops.h index 2a420ac8319..3fe64e82e9f 100644 --- a/lib/intprops.h +++ b/lib/intprops.h @@ -3,19 +3,18 @@ Copyright (C) 2001-2021 Free Software Foundation, Inc. This program is free software: you can redistribute it and/or modify it - under the terms of the GNU General Public License as published - by the Free Software Foundation; either version 3 of the License, or + under the terms of the GNU Lesser General Public License as published + by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - GNU General Public License for more details. + GNU Lesser General Public License for more details. - You should have received a copy of the GNU General Public License + You should have received a copy of the GNU Lesser General Public License along with this program. If not, see <https://www.gnu.org/licenses/>. */ -/* Written by Paul Eggert. */ #ifndef _GL_INTPROPS_H #define _GL_INTPROPS_H @@ -133,7 +132,8 @@ operators might not yield numerically correct answers due to arithmetic overflow. They do not rely on undefined or implementation-defined behavior. Their implementations are simple - and straightforward, but they are a bit harder to use than the + and straightforward, but they are harder to use and may be less + efficient than the INT_<op>_WRAPV, INT_<op>_OK, and INT_<op>_OVERFLOW macros described below. Example usage: @@ -158,6 +158,9 @@ must have minimum value MIN and maximum MAX. Unsigned types should use a zero MIN of the proper type. + Because all arguments are subject to integer promotions, these + macros typically do not work on types narrower than 'int'. + These macros are tuned for constant MIN and MAX. For commutative operations such as A + B, they are also tuned for constant B. */ @@ -339,9 +342,15 @@ arguments should not have side effects. The WRAPV macros are not constant expressions. They support only - +, binary -, and *. Because the WRAPV macros convert the result, - they report overflow in different circumstances than the OVERFLOW - macros do. + +, binary -, and *. + + Because the WRAPV macros convert the result, they report overflow + in different circumstances than the OVERFLOW macros do. For + example, in the typical case with 16-bit 'short' and 32-bit 'int', + if A, B and R are all of type 'short' then INT_ADD_OVERFLOW (A, B) + returns false because the addition cannot overflow after A and B + are converted to 'int', whereas INT_ADD_WRAPV (A, B, &R) returns + true or false depending on whether the sum fits into 'short'. These macros are tuned for their last input argument being a constant. |