CODEWITHSUNDEEP
cprintflanguage-lawyerc99c11
ddbug
ddbug

Reputation: 1559

Is printf length modifier %L standard (or future standard)?

Per cppreference.com the length modifier %L is valid only for float types. But modern GNU compiler & library seems to accept it also for integers as synonym of %ll (long long). Is there a chance that cppreference mistakes on this? Or is %L for integers going to become standard in future?

Upvotes: 1

Views: 293

Answers (2)

ad absurdum
ad absurdum

Reputation: 21360

The valid length modifiers are listed in §7.21.6.1 7 of the C11 Standard.

The only mention of L as a length modifier in the Standard is for long double types:

L Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a long double argument.

Further, there is no mention of this in §7.31 Future Library Directions:

7.31.11 Input/output < stdio.h >

  • 1 Lowercase letters may be added to the conversion specifiers and length modifiers in fprintf and fscanf. Other characters may be used in extensions.

  • 2 The use of ungetc on a binary stream where the file position indicator is zero prior to the call is an obsolescent feature.

And, the same use of L holds in the POSIX Standard: L is a length modifier to be used with long double types only.

Upvotes: 3

user2371524
user2371524

Reputation:

From the latest C11 draft N1570, §7.21.6.1 section 7:

L -- Specifies that a following a, A, e, E, f, F, g, or G conversion specifier applies to a long double argument.

So your source is correct, L as a length modifier is only defined for floating point conversions. I wouldn't expect this to change in future versions, as there's simply no need. Just use l and ll as appropriate.

Upvotes: 4

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