Perl API 类型的 printf 格式说明符

Question

Are there macros that provide the correct printf format specifiers for IV , UV , STRLEN , Size_t and SSize_t ? None are listed in perlapi .

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C provides macros for the format specifiers for the types provided by stdint.h , such as uint32_t .

#include <inttypes.h>
#include <stdint.h>

uint32_t i = ...;
printf("i = %" PRIu32 "\n", i);

Is there something similar to PRIu32 for IV , UV , STRLEN , Size_t and SSize_t ?

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The larger problem is that I'm trying to suggest a fix for the following compilation warnings produced when installing Sort::Key on Ubuntu on Windows Subsystem for Linux:

Key.xs: In function ‘_keysort’:
Key.xs:237:12: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘IV {aka long int}’ [-Wformat=]
      croak("unsupported sort type %d", type);
            ^~~~~~~~~~~~~~~~~~~~~~~~~~
Key.xs: In function ‘_multikeysort’:
Key.xs:547:9: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘STRLEN {aka long unsigned int}’ [-Wformat=]
   croak("wrong number of results returned "
         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Key.xs:547:9: warning: format ‘%d’ expects argument of type ‘int’, but argument 3 has type ‘IV {aka long int}’ [-Wformat=]

Answer 1

• For UV , the following macros exist:

  • UVuf (decimal)
  • UVof (octal)
  • UVxf (lc hex)
  • UVXf (uc hex)

• For IV , the following macro exists:

  • IVdf (decimal)

• For NV , the following macros exist:

  • NVef (" %e -ish")
  • NVff (" %f -ish")
  • NVgf (" %g -ish")

• For Size_t and STRLEN , use the builtin z length modifier. ^[1]

  • %zu (decimal)
  • %zo (octal)
  • %zx (lc hex)
  • %zX (uc hex)

• For SSize_t , use the builtin z length modifier. ^[1]

  • %zd (decimal)

For example,

IV iv      = ...;
STRLEN len = ...;

croak("iv=%" IVdf " len=%zu", iv, len);

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1. While Size_t and SSize_t are configurable, they're never different from size_t and ssize_t in practice, and STRLEN is a typedef for Size_t .

Answer 2

If Size_t is the same as size_t , then %zu is correct.

STRLEN is likely, but not certain, to be the same as size_t .

If SSize_t is the same as ssize_t , then %zd is probably correct (it's complicated).

For other types, if you don't know what predefined type they correspond to, convert to a known type. Knowing the signedness helps. For example:

some_unknown_signed_integer_type n = 42;
some_unknown_unsigned_integer_type x = 128;
printf("n = %jd\n", (intmax_t)n);
printf("x = %ju\n", (uintmax_t)x);

intmax_t and uintmax_t are defined in <stdint.h> .

You can get away with converting to long or unsigned long and using %ld or %lu , for example, if you happen to know that the type is no wider than long or unsigned long .