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**Section:** 17.4 [cstdint] **Status:** Open
**Submitter:** Thomas Köppe **Opened:** 2016-11-12 **Last modified:** 2019-03-26

**Priority: **3

**View all other** issues in [cstdint].

**View all issues with** Open status.

**Discussion:**

I would like clarification from LWG regarding the various limit macros like `INT_8_MIN` in `<cstdint>`,
in pursuit of editorial cleanup of this header's synopsis. I have two questions:

At present, macros like

`INT_8_MIN`that correspond to the optional type`int8_t`are required (unconditionally), whereas the underlying type to which they appertain is only optional. Is this deliberate? Should the macros also be optional?Is it deliberate that C++ only specifies sized aliases for the sizes 8, 16, 32 and 64, whereas the corresponding C header allows type aliases and macros for arbitrary sizes for implementations that choose to provide extended integer types? Is the C++ wording more restrictive by accident?

*[2017-01-27 Telecon]*

Priority 3

*[2017-03-04, Kona]*

C11 ties the macro names to the existence of the types. Marshall to research the second question.

Close 2764 as a duplicate of this issue.

*[2017-03-18, Thomas comments and provides wording]*

This is as close as I can get to the C wording without resolving part (a) of the issue (whether we deliberately don't
allow sized type aliases for sizes other than 8, 16, 32, 64, a departure from C). Once we resolve part (a), we need
to revisit `<cinttypes>` and fix up the synopsis (perhaps to get rid of `N`) and add similar
wording as the one below to make the formatting macros for the fixed-width types optional. For historical interest,
this issue is related to LWG 553 and LWG 841.

*[2016-07, Toronto Saturday afternoon issues processing]*

Status to Open

This wording is relative to N4640.

Append the following content to 17.4.1 [cstdint.syn] p2:

-2- The header defines all types and macros the same as the C standard library header

<stdint.h>. In particular, for each of the fixed-width types (int8_t,int16_t,int32_t,int64_t,uint8_t,uint16_t,uint32_t,uint64_t) the type alias and the corresponding limit macros are defined if and only if the implementation provides the corresponding type.

*[2017-10-21, Thomas Köppe provides improved wording]*

**Previous resolution [SUPERSEDED]:**

This wording is relative to N4687.

Change 17.4.1 [cstdint.syn], header

<cstdint>synopsis, as indicated:[…] using int64_t =signed integer type;// optionalusing intN_t =see below;// optional, see below[…] using int_fast64_t =signed integer type; using int_fastN_t =see below;// optional, see below[…] using int_least64_t =signed integer type; using int_leastN_t =see below;// optional, see below[…] using uint64_t =unsigned integer type;// optionalusing uintN_t =see below;// optional, see below[…] using uint_fast64_t =unsigned integer type; using uint_fastN_t =see below;// optional, see below[…] using uint_least64_t =unsigned integer type; using uint_leastN_t =see below;// optional, see belowusing uintmax_t =unsigned integer type; using uintptr_t =unsigned integer type;// optional#define INT_N_MINsee below; #define INT_N_MAXsee below; #define UINT_N_MAXsee below; #define INT_FASTN_MINsee below; #define INT_FASTN_MAXsee below; #define UINT_FASTN_MAXsee below; #define INT_LEASTN_MINsee below; #define INT_LEASTN_MAXsee below; #define UINT_LEASTN_MAXsee below; #define INTMAX_MINsee below; #define INTMAX_MAXsee below; #define UINTMAX_MAXsee below; #define INTPTR_MINsee below; #define INTPTR_MAXsee below; #define UINTPTR_MAXsee below; #define PTRDIFF_MINsee below; #define PTRDIFF_MAXsee below; #define SIZE_MAXsee below; #define SIGATOMIC_MINsee below; #define SIGATOMIC_MAXsee below; #define WCHAR_MINsee below; #define WCHAR_MAXsee below; #define WINT_MINsee below; #define WINT_MAXsee below; #define INTN_C(value)see below; #define UINTN_C(value)see below; #define INTMAX_C(value)see below; #define UINTMAX_C(value)see below;

~~-1- The header also defines numerous macros of the form:~~~~INT_[FAST LEAST]{8 16 32 64}_MIN [U]INT_[FAST LEAST]{8 16 32 64}_MAX INT{MAX PTR}_MIN [U]INT{MAX PTR}_MAX {PTRDIFF SIG_ATOMIC WCHAR WINT}{_MAX _MIN} SIZE_MAX~~

~~plus function macros of the form:~~~~[U]INT{8 16 32 64 MAX}_C~~-2- The header defines all types and macros the same as the C standard library header

<stdint.h>. See also: ISO C 7.20-?- In particular, all types that use the placeholder

are optional whenNis not 8, 16, 32 or 64. The exact-width typesNintandN_tuintforN_t= 8, 16, 32, 64 are also optional; however, if an implementation provides integer types with the corresponding width, no padding bits, and (for the signed types) that have a two's complement representation, it defines the corresponding typedef names. Only those macros are defined that correspond to typedef names that the implementation actually provides. [NNote:The macrosINTandN_CUINTcorrespond to the typedef namesN_Cint_leastandN_tuint_least, respectively. —N_tend note]Change 29.12.2 [cinttypes.syn] as indicated:

#define PRId~~N~~Nsee below#define PRIi~~N~~Nsee below#define PRIo~~N~~Nsee below#define PRIu~~N~~Nsee below#define PRIx~~N~~Nsee below#define PRIX~~N~~Nsee below#define SCNd~~N~~Nsee below#define SCNi~~N~~Nsee below#define SCNo~~N~~Nsee below#define SCNu~~N~~Nsee below#define SCNx~~N~~Nsee below#define PRIdLEAST~~N~~Nsee below#define PRIiLEAST~~N~~Nsee below#define PRIoLEAST~~N~~Nsee below#define PRIuLEAST~~N~~Nsee below#define PRIxLEAST~~N~~Nsee below#define PRIXLEAST~~N~~Nsee below#define SCNdLEAST~~N~~Nsee below#define SCNiLEAST~~N~~Nsee below#define SCNoLEAST~~N~~Nsee below#define SCNuLEAST~~N~~Nsee below#define SCNxLEAST~~N~~Nsee below#define PRIdFAST~~N~~Nsee below#define PRIiFAST~~N~~Nsee below#define PRIoFAST~~N~~Nsee below#define PRIuFAST~~N~~Nsee below#define PRIxFAST~~N~~Nsee below#define PRIXFAST~~N~~Nsee below#define SCNdFAST~~N~~Nsee below#define SCNiFAST~~N~~Nsee below#define SCNoFAST~~N~~Nsee below#define SCNuFAST~~N~~Nsee below#define SCNxFAST~~N~~Nsee below[…]-1- The contents and meaning of the header

<cinttypes>[…]-?- In particular, macros that use the placeholder

are defined if and only if the implementation actually provides the corresponding typedef name in 17.4.1 [cstdint.syn], and moreover, theNfscanfmacros are provided unless the implementation does not have a suitablefscanflength modifier for the type.

*[2018-04-03; Geoffrey Romer suggests improved wording]*

**Previous resolution [SUPERSEDED]:**

This wording is relative to N4727.

Change 17.4.1 [cstdint.syn], header

<cstdint>synopsis, as indicated:[…] using int64_t =signed integer type;// optionalusing intN_t =see below;// optional, see below[…] using int_fast64_t =signed integer type; using int_fastN_t =see below;// optional, see below[…] using int_least64_t =signed integer type; using int_leastN_t =see below;// optional, see below[…] using uint64_t =unsigned integer type;// optionalusing uintN_t =see below;// optional, see below[…] using uint_fast64_t =unsigned integer type; using uint_fastN_t =see below;// optional, see below[…] using uint_least64_t =unsigned integer type; using uint_leastN_t =see below;// optional, see belowusing uintmax_t =unsigned integer type; using uintptr_t =unsigned integer type;// optional#define INT_N_MINsee below; #define INT_N_MAXsee below; #define UINT_N_MAXsee below; #define INT_FASTN_MINsee below; #define INT_FASTN_MAXsee below; #define UINT_FASTN_MAXsee below; #define INT_LEASTN_MINsee below; #define INT_LEASTN_MAXsee below; #define UINT_LEASTN_MAXsee below; #define INTMAX_MINsee below; #define INTMAX_MAXsee below; #define UINTMAX_MAXsee below; #define INTPTR_MINsee below; #define INTPTR_MAXsee below; #define UINTPTR_MAXsee below; #define PTRDIFF_MINsee below; #define PTRDIFF_MAXsee below; #define SIZE_MAXsee below; #define SIGATOMIC_MINsee below; #define SIGATOMIC_MAXsee below; #define WCHAR_MINsee below; #define WCHAR_MAXsee below; #define WINT_MINsee below; #define WINT_MAXsee below; #define INTN_C(value)see below; #define UINTN_C(value)see below; #define INTMAX_C(value)see below; #define UINTMAX_C(value)see below;

~~-1- The header also defines numerous macros of the form:~~~~INT_[FAST LEAST]{8 16 32 64}_MIN [U]INT_[FAST LEAST]{8 16 32 64}_MAX INT{MAX PTR}_MIN [U]INT{MAX PTR}_MAX {PTRDIFF SIG_ATOMIC WCHAR WINT}{_MAX _MIN} SIZE_MAX~~

~~plus function macros of the form:~~~~[U]INT{8 16 32 64 MAX}_C~~-2- The header defines all types and macros the same as the C standard library header

<stdint.h>. See also: ISO C 7.20-?- In particular, all types that use the placeholder

are optional whenNis not 8, 16, 32 or 64. The exact-width typesNintandN_tuintforN_t= 8, 16, 32, 64 are also optional; however, if an implementation provides integer types with the corresponding width, no padding bits, and (for the signed types) that have a two's complement representation, it defines the corresponding typedef names. Only those macros are defined that correspond to typedef names that the implementation actually provides. [NNote:The macrosINTandN_CUINTcorrespond to the typedef namesN_Cint_leastandN_tuint_least, respectively. —N_tend note]Change 29.12.2 [cinttypes.syn] as indicated:

#define PRId~~N~~Nsee below#define PRIi~~N~~Nsee below#define PRIo~~N~~Nsee below#define PRIu~~N~~Nsee below#define PRIx~~N~~Nsee below#define PRIX~~N~~Nsee below#define SCNd~~N~~Nsee below#define SCNi~~N~~Nsee below#define SCNo~~N~~Nsee below#define SCNu~~N~~Nsee below#define SCNx~~N~~Nsee below#define PRIdLEAST~~N~~Nsee below#define PRIiLEAST~~N~~Nsee below#define PRIoLEAST~~N~~Nsee below#define PRIuLEAST~~N~~Nsee below#define PRIxLEAST~~N~~Nsee below#define PRIXLEAST~~N~~Nsee below#define SCNdLEAST~~N~~Nsee below#define SCNiLEAST~~N~~Nsee below#define SCNoLEAST~~N~~Nsee below#define SCNuLEAST~~N~~Nsee below#define SCNxLEAST~~N~~Nsee below#define PRIdFAST~~N~~Nsee below#define PRIiFAST~~N~~Nsee below#define PRIoFAST~~N~~Nsee below#define PRIuFAST~~N~~Nsee below#define PRIxFAST~~N~~Nsee below#define PRIXFAST~~N~~Nsee below#define SCNdFAST~~N~~Nsee below#define SCNiFAST~~N~~Nsee below#define SCNoFAST~~N~~Nsee below#define SCNuFAST~~N~~Nsee below#define SCNxFAST~~N~~Nsee below[…]-1- The contents and meaning of the header

<cinttypes>[…]-?-

PRImacros that use the placeholderare defined if and only if the implementation actually provides the corresponding typedef name in 17.4.1 [cstdint.syn].NSCNmacros that use the placeholderare defined if and only if the implementation actually provides the corresponding typedef name and the implementation has a suitableNfscanflength modifier for the type.

*[2019-03-11; Reflector review and improved wording]*

Wording simplifications due to new general two's complement requirements of integer types; removal of wording redundancies and applying some typo fixes in macro names.

*[2019-03-16; Daniel comments and updates wording]*

Hubert Tong pointed out that we do not have a statement about `[U]INTPTR_{MIN|MAX}` being optional.
Interestingly, the C11 Standard does not say directly that the `[U]INTPTR_{MIN|MAX}` macros are optional,
but this follows indirectly from the fact that `intptr_t` and `uintptr_t` are indeed optional.
The updated wording therefore realizes Hubert's suggestion.

In addition, the reference document has been rebased to N4810, because that draft version contains an editorial change, which renames the term "range exponent" of integer types to "width", which is the vocabulary used below and also matches C's use.

Finally, Hubert Tong suggested the following rewording replacements of

If and only if the implementation defines such a typedef name, it also defines the corresponding macros.

to:

Each of the macros listed in this subclause is defined if and only if the implementation defines the corresponding typedef name.

and of

PRImacros that use the placeholder N are defined if and only if the implementation actually defines the corresponding typedef name in 17.4.1 [cstdint.syn].SCNmacros that use the placeholderare defined if and only if the implementation actually defines the corresponding typedef name and the implementation has a suitableNfscanflength modifier for the type.

to:

Each of the macros listed in this subclause is defined if and only if the implementation actually defines the corresponding typedef name in 17.4.1 [cstdint.syn].

Those changes have been applied as well.

*[2019-03-26; Reflector discussion and minor wording update]*

Geoffrey pointed out that the revised wording has the effect that it requires an implementation to define `SCN`
macros for all mentioned typedefs, but the C11 standard says "the corresponding `fscanf` macros shall be
defined unless the implementation does not have a suitable `fscanf` length modifier for the type.". An additional
wording update repairs this problem below.

**Proposed resolution:**

This wording is relative to N4810.

Change 17.4.1 [cstdint.syn], header

`<cstdint>`synopsis, as indicated:[…] using int64_t =

*signed integer type*;*// optional*using int*N*_t =*see below*;*// optional, see below*[…] using int_fast64_t =*signed integer type*; using int_fast*N*_t =*see below*;*// optional, see below*[…] using int_least64_t =*signed integer type*; using int_least*N*_t =*see below*;*// optional, see below*[…] using uint64_t =*unsigned integer type*;*// optional*using uint*N*_t =*see below*;*// optional, see below*[…] using uint_fast64_t =*unsigned integer type*; using uint_fast*N*_t =*see below*;*// optional, see below*[…] using uint_least64_t =*unsigned integer type*; using uint_least*N*_t =*see below*;*// optional, see below*using uintmax_t =*unsigned integer type*; using uintptr_t =*unsigned integer type*;*// optional*#define INT*N*_MIN*see below*#define INT*N*_MAX*see below*#define UINT*N*_MAX*see below*#define INT_FAST*N*_MIN*see below*#define INT_FAST*N*_MAX*see below*#define UINT_FAST*N*_MAX*see below*#define INT_LEAST*N*_MIN*see below*#define INT_LEAST*N*_MAX*see below*#define UINT_LEAST*N*_MAX*see below*#define INTMAX_MIN*see below*#define INTMAX_MAX*see below*#define UINTMAX_MAX*see below*#define INTPTR_MIN*optional, see below*#define INTPTR_MAX*optional, see below*#define UINTPTR_MAX*optional, see below*#define PTRDIFF_MIN*see below*#define PTRDIFF_MAX*see below*#define SIZE_MAX*see below*#define SIG_ATOMIC_MIN*see below*#define SIG_ATOMIC_MAX*see below*#define WCHAR_MIN*see below*#define WCHAR_MAX*see below*#define WINT_MIN*see below*#define WINT_MAX*see below*#define INT*N*_C(value)*see below*#define UINT*N*_C(value)*see below*#define INTMAX_C(value)*see below*#define UINTMAX_C(value)*see below*~~-1- The header also defines numerous macros of the form:~~~~INT_[FAST LEAST]{8 16 32 64}_MIN [U]INT_[FAST LEAST]{8 16 32 64}_MAX INT{MAX PTR}_MIN [U]INT{MAX PTR}_MAX {PTRDIFF SIG_ATOMIC WCHAR WINT}{_MAX _MIN} SIZE_MAX~~~~plus function macros of the form:~~~~[U]INT{8 16 32 64 MAX}_C~~-2- The header defines all types and macros the same as the C standard library header

`<stdint.h>`. See also: ISO C 7.20-?- All types that use the placeholder

are optional when*N*is not 8, 16, 32 or 64. The exact-width types*N*`int`and*N*_t`uint`for*N*_t= 8, 16, 32, 64 are also optional; however, if an implementation defines integer types with the corresponding width and no padding bits, it defines the corresponding typedef names. Each of the macros listed in this subclause is defined if and only if the implementation defines the corresponding typedef name. [*N**Note:*The macros`INT`and*N*_C`UINT`correspond to the typedef names*N*_C`int_least`and*N*_t`uint_least`, respectively. —*N*_t*end note*]Change 29.12.2 [cinttypes.syn] as indicated:

#define PRId

~~N~~*N**see below*#define PRIi~~N~~*N**see below*#define PRIo~~N~~*N**see below*#define PRIu~~N~~*N**see below*#define PRIx~~N~~*N**see below*#define PRIX~~N~~*N**see below*#define SCNd~~N~~*N**see below*#define SCNi~~N~~*N**see below*#define SCNo~~N~~*N**see below*#define SCNu~~N~~*N**see below*#define SCNx~~N~~*N**see below*#define PRIdLEAST~~N~~*N**see below*#define PRIiLEAST~~N~~*N**see below*#define PRIoLEAST~~N~~*N**see below*#define PRIuLEAST~~N~~*N**see below*#define PRIxLEAST~~N~~*N**see below*#define PRIXLEAST~~N~~*N**see below*#define SCNdLEAST~~N~~*N**see below*#define SCNiLEAST~~N~~*N**see below*#define SCNoLEAST~~N~~*N**see below*#define SCNuLEAST~~N~~*N**see below*#define SCNxLEAST~~N~~*N**see below*#define PRIdFAST~~N~~*N**see below*#define PRIiFAST~~N~~*N**see below*#define PRIoFAST~~N~~*N**see below*#define PRIuFAST~~N~~*N**see below*#define PRIxFAST~~N~~*N**see below*#define PRIXFAST~~N~~*N**see below*#define SCNdFAST~~N~~*N**see below*#define SCNiFAST~~N~~*N**see below*#define SCNoFAST~~N~~*N**see below*#define SCNuFAST~~N~~*N**see below*#define SCNxFAST~~N~~*N**see below*[…]-1- The contents and meaning of the header

`<cinttypes>`[…]-?- Each of the

`PRI`macros listed in this subclause is defined if and only if the implementation defines the corresponding typedef name in 17.4.1 [cstdint.syn]. Each of the`SCN`macros listed in this subclause is defined if and only if the implementation defines the corresponding typedef name in 17.4.1 [cstdint.syn] and has a suitable`fscanf`length modifier for the type.