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Re: INTx_C/UINTx_C definitions result type
On Sun, Dec 05, 2010 at 22:11:32 +0100, Nicolas Joly wrote:
> I just noted that INTx_C/UINTx_C macros does not seems to return
> costants of the specified `uint_leastx_t' type as expected ...
> 220.127.116.11 Macros for minimum-width integer constants
> Actually only the smallest version (x < 32) suffers from this and
> sizeof(INT8_C(0)) = 4 differs from sizeof(int_least8_t) = 1.
> Any drawbacks to be expected with the following patch that adds casts
> for the corresponding types ?
I think your patch is not correct. What is the problem you are trying
My old copy of ISO C FDIS says
7.18.4 Macros for integer constants
[#1] The following function-like macros220) expand to
integer constants suitable for initializing objects that
have integer types corresponding to types defined in
<stdint.h>. Each macro name corresponds to a similar type
name in 18.104.22.168 or 22.214.171.124.
126.96.36.199 Macros for minimum-width integer constants
[#1] Each of the following macros expands to an integer
constant having the value specified by its argument and a
type with at least the specified width.221)
[#2] The macro INTN_C(value) shall expand to a signed
integer constant with the specified value and type
int_leastN_t. The macro UINTN_C(value) shall expand to an
unsigned integer constant with the specified value and type
Note that the requirement are: "suitable for initializing" in 7.18.4#1
and "at least the specified width" in 188.8.131.52#1.
184.108.40.206#2 says "and type int_leastN_t", which is confusing, but I
think it's the sloppy wording in #2.
Current draft http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1539.pdf
seems to clarify that properly:
7.20.4 Macros for integer constants
1 The following function-like macros expand to integer constants
suitable for initializing objects that have integer types
corresponding to types defined in <stdint.h>. Each macro name
corresponds to a similar type name in 220.127.116.11 or 18.104.22.168.
3 Each invocation of one of these macros shall expand to an integer
constant expression suitable for use in #if preprocessing
directives. The type of the expression shall have the same type as
would an expression of the corresponding type converted according to
the integer promotions. The value of the expression shall be that of
22.214.171.124 Macros for minimum-width integer constants
1 The macro INTN_C(value) shall expand to an integer constant
expression corresponding to the type int_leastN_t. The macro
UINTN_C(value) shall expand to an integer constant expression
corresponding to the type uint_leastN_t. For example, if
uint_least64_t is a name for the type unsigned long long int, then
UINT64_C(0x123) might expand to the integer constant 0x123ULL.
Note in particular that 7.20.4#3 now explicitly talks about integer
promotions and mandates that the macro could be used in #if.
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