I was wondering on how to use this function, because I get an error when I do this:
#define INT_ADD_OVERFLOW_P(a, b) \
__builtin_add_overflow_p (a, b, (__typeof__ ((a) + (b))) 0);
#include <stdio.h>
#include <assert.h>
__int main()
{
int x1 = -1073741826;
int y1 = -1073741826;
int z1 = x1+y1;
INT_ADD_OVERFLOW_P ( x1, y1);
printf("%d\n",z1);
return 0;
}
Compile_OUTPUT:
gcc -c -Wall -D DEBUG tempFile.c
gcc tempFile.o -o tempFile
Makefile:8: recipe for target 'tempFile' failed//new error after update
Compile_ERROR:
tempFile.c: In function ‘main’:
tempFile.c:10:1: warning: implicit declaration of function ‘__builtin_add_overflow_p’ [-Wimplicit-function-declaration]
tempFile.o: In function `main':
tempFile.c:(.text+0x44): undefined reference to `__builtin_add_overflow_p'
collect2: ld returned 1 exit status
make: *** [tempFile] Error 1
Here is a link to the functions I want to use:
https://gcc.gnu.org/onlinedocs/gcc/Integer-Overflow-Builtins.html
Here is the makefile that i'm using:
compiler=gcc
CFLAGS=-c -Wall -D DEBUG
programname=tempFile
all: $(programname)
$(programname): $(programname).o
$(compiler) $(programname).o -o $(programname)
$(programname).o: $(programname).c
$(compiler) $(CFLAGS) $(programname).c
clean:
rm *o $(programname)
Builtin functions of GCC compiler. Bitwise Operators in C/C++ Python Bitwise Operators. Bits manipulation (Important tactics) Little and Big Endian Mystery.
int__builtin_ffs (unsigned int x) Returns one plus the index of the least significant 1-bit of x, or if x is zero, returns zero. int__builtin_clz (unsigned int x) Returns the number of leading 0-bits in x, starting at the most significant bit position. If x is 0, the result is undefined.
__builtin_add_overflow_p
is supported by GCC 7 that has not been released yet
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