uint64_t的运算出错问题各位大神请看下面的程序，我的问题在注释里//编译环境：codeblocks+gcc #include st
uint64_t的运算出错问题
各位大神请看下面的程序，我的问题在注释里
//编译环境：codeblocks+gcc
#include <stdio.h>
#include <stdint.h>
int Fun()
{
uint64_t y;
uint32_t x1, x2;
y = 3000 * 24000000 / 1000;
printf("0x%llX\n", y);//输出错误结果：0xFFFFFFFFFFF08554 ，Why??? int64位不能正确运算吗？
x1 = (uint32_t)(y & 0xFFFFFFFF);
x2 = (uint32_t)(y >> 32);
printf("0x%X,0x%X \n", x1, x2);//输出错误结果：0xFFF08554, 0xFFFFFFFF
y = 3000 * (24000000 / 1000);
printf("0x%llX\n", y);//输出正确结果： 0x44AA200
x1 = (uint32_t)(y & 0xFFFFFFFF);
x2 = (uint32_t)(y >> 32);
printf("0x%X,0x%X \n", x1, x2);//正确结果 ：0x44AA200， 0x0
}
int main()
{
Fun();
}
[解决办法]常量也有类型！
C++ Integer Constants
Integer constants are constant data elements that have no fractional parts or exponents. They always begin with a digit. You can specify integer constants in decimal, octal, or hexadecimal form. They can specify signed or unsigned types and long or short types.
Syntax
integer-constant :
decimal-constant integer-suffixopt
octal-constant integer-suffixopt
hexadecimal-constant integer-suffixopt
'c-char-sequence'
decimal-constant :
nonzero-digit
decimal-constant digit
octal-constant :
0
octal-constant octal-digit
hexadecimal-constant :
0x hexadecimal-digit
0X hexadecimal-digit
hexadecimal-constant hexadecimal-digit
nonzero-digit : one of
1 2 3 4 5 6 7 8 9
octal-digit : one of
0 1 2 3 4 5 6 7
hexadecimal-digit : one of
0 1 2 3 4 5 6 7 8 9
a b c d e f
A B C D E F
integer-suffix :
unsigned-suffix long-suffixopt
long-suffix unsigned-suffixopt
unsigned-suffix : one of
u U
long-suffix : one of
l L
64-bit integer-suffix :
i64
To specify integer constants using octal or hexadecimal notation, use a prefix that denotes the base. To specify an integer constant of a given integral type, use a suffix that denotes the type.
To specify a decimal constant, begin the specification with a nonzero digit. For example:
int i = 157; // Decimal constant
int j = 0198; // Not a decimal number; erroneous octal constant
int k = 0365; // Leading zero specifies octal constant, not decimal
To specify an octal constant, begin the specification with 0, followed by a sequence of digits in the range 0 through 7. The digits 8 and 9 are errors in specifying an octal constant. For example:
int i = 0377; // Octal constant
int j = 0397; // Error: 9 is not an octal digit
To specify a hexadecimal constant, begin the specification with 0x or 0X (the case of the “x” does not matter), followed by a sequence of digits in the range 0 through 9 and a (or A) through f (or F). Hexadecimal digits a (or A) through f (or F) represent values in the range 10 through 15. For example:
int i = 0x3fff; // Hexadecimal constant
int j = 0X3FFF; // Equal to i
To specify an unsigned type, use either the u or U suffix. To specify a long type, use either the l or L suffix. For example:
unsigned uVal = 328u; // Unsigned value
long lVal = 0x7FFFFFL; // Long value specified
// as hex constant
unsigned long ulVal = 0776745ul; // Unsigned long value
[解决办法]
3000和3000i64和3000ui64不是一回事！
[解决办法]
y = (uint64_t)3000 * (uint64_t)24000000 / 1000;
C语言基础不过关。
