Languages/C/inttypes
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=== Microsoft Visual C++ === | === Microsoft Visual C++ === | ||
Here is a suitable [http://msinttypes.googlecode.com/svn/trunk/stdint.h stdint.h] file. | Here is a suitable [http://msinttypes.googlecode.com/svn/trunk/stdint.h stdint.h] file. | ||
+ | |||
+ | == Bit shift operators and signed integers == | ||
+ | |||
+ | What is the value of <code>((int32_t)-1) >> 1</code> and <code>((int32_t)-1) << 1</code> ? | ||
+ | -> The result is implementation dependent. | ||
+ | |||
+ | Conclusion : Don't use shift operators on signed integers! | ||
+ | |||
[[Category:Languages]] [[Category:C]] | [[Category:Languages]] [[Category:C]] |
Revision as of 14:52, 12 February 2013
|
Integer types in C (and C++)
The C language defines a lot of integer types (char
, short
, int
, unsigned int
, long
, long long
,...)
but unfortunately their size are implementation dependent (vendor/platform/compiler).
Writing programs in a portable manner requires the use of known size integers.
C99 integer sizes
Recent compilers provide the <stdint.h> file that defines a lot of integer types, and because this is a standard, new code should no more use the "old" HEVs coding style.
C99 type | Old HEVs type | size (bits) | minimum value (define) | minimum value (numeric) | maximum value (define) | maximum value (numeric) |
uint8_t | UINT8 | 8 | - | 0 | UINT8_MAX | 255 |
uint16_t | UINT16 | 16 | - | 0 | UINT16_MAX | 65'535 |
uint32_t | UINT32 | 32 | - | 0 | UINT32_MAX | 4'294'967'295 |
uint64_t | UINT64 | 64 | - | 0 | UINT64_MAX | 18'446'744'073'709'551'615 |
int8_t | INT8 | 8 | INT8_MIN | -128 | UINT8_MAX | 127 |
int16_t | INT16 | 16 | INT16_MIN | -3'2768 | UINT16_MAX | 32'767 |
int32_t | INT32 | 32 | INT32_MIN | -2'147'483'648 | UINT32_MAX | 2'147'483'647 |
int64_t | INT64 | 64 | INT64_MIN | -9'223'372'036'854'775'807 | UINT64_MAX | 9'223'372'036'854'775'807 |
C++ support
C++ users should use <stdint.h> C++11 will introduce the <cstdint> header.
Compiler support & remarks
GCC
gcc
fully supports <stdint.h>.
HI TECH PIC18 C compiler
Since version 9.65, this compiler supports <stdint.h>, without the (u)int64_t
.
Microchip XC8 compiler
This compiler has the <sdtint.h> file.
Since version 9.65, this compiler supports <stdint.h>, without the (u)int64_t
.
IAR - MSP430
This compiler supports <stdint.h>.
Microsoft Visual C++
Here is a suitable stdint.h file.
Bit shift operators and signed integers
What is the value of ((int32_t)-1) >> 1
and ((int32_t)-1) << 1
?
-> The result is implementation dependent.
Conclusion : Don't use shift operators on signed integers!