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ID Category Severity Type Date Submitted Last Update
0001413 [Issue 8 drafts] Shell and Utilities Objection Error 2020-10-24 22:01 2024-06-11 09:12
Reporter philip-guenther View Status public  
Assigned To
Priority normal Resolution Accepted As Marked  
Status Closed   Product Version Draft 1.1
Name Philip Guenther
Organization OpenBSD
User Reference
Section printf's APPLICATION USAGE
Page Number 3038
Line Number 102845 - 102848
Final Accepted Text See Note: 0005276
Summary 0001413: incorrect description of how a hexadecimal character constant can be terminated in ISO C
Description The text says:

> In the ISO C standard, the "##" concatenation
> operator can be used to terminate a constant and follow it with a hexadecimal character to be
> written. In the shell, concatenation occurs before the printf utility has a chance to parse the end
> of the hexadecimal constant.

The ## operator is neither necessary nor sufficient. All that's needed is use of string literal concatenation.

Indeed, this was an example in (at least) drafts of the C99 standard, in the specification of string literals lexical elements:

# EXAMPLE This pair of adjacent character string literals
#
# "\x12" "3"
#
# produces a single character string literal containing the two characters whose values are '\x12' and '3',
# because escape sequences are converted into single members of the execution character set just prior to
# adjacent string literal concatenation.
Desired Action Replace the sentence:
  In the ISO C standard, the "##" concatenation operator can be used to terminate a constant and follow it with a hexadecimal character to be written.

With something like:
  In the ISO C standard, the constant and its following hexadecimal character can be placed in separate string literals as escape sequence processing occurs before string literal concatenation.

(I'm not really happy with that phrasing; better suggestions welcome!)
Tags issue8
Attached Files

- Relationships
child of 0000249Closedajosey 1003.1(2008)/Issue 7 Add standard support for $'...' in shell 

-  Notes
(0005248)
nick (manager)
2021-02-18 17:12

 (TC2 page and line numbers) change page 3115 line 104182-104185, after 0000249 is resolved:
        
In the ISO C standard, the "##" concatenation operator can be used to terminate a constant and follow it with a hexadecimal character to be written. In the shell, concatenation occurs before the printf utility has a chance to parse the end of the hexadecimal constant.

to:
      
Note however that a <tt>$'...'</tt> string may be used to embed hexadecimal constants in a format string in a portable way.
(0005274)
mirabilos (reporter)
2021-03-15 20:53

 I don’t quite get this. In $'…' strings, \x123 is also unspecified (some current implementations make this into \x23 or even \u0123).

Maybe as $'\x12'3 or, more generally, $'\x12'$'3' … hmm, but that’s not obvious from the wording.
(0005276)
geoffclare (manager)
2021-03-16 10:01

 I see your point. Perhaps it would be better to keep the part about concatenation (with corrected wording) and say that in the shell $'...' can be used in a similar way. Something like:

On 2018 edition page 3115 line 104182-104185, after 0000249 is resolved change:
In the ISO C standard, the "##" concatenation operator can be used to terminate a constant and follow it with a hexadecimal character to be written. In the shell, concatenation occurs before the printf utility has a chance to parse the end of the hexadecimal constant.
to:
In the ISO C standard, string literal concatenation can be used to terminate a constant and follow it with a hexadecimal character to be written. In the shell, similar concatenation can be done using <tt>$'...'</tt> so that the shell converts the hexadecimal sequence before it executes printf.
(0006011)
geoffclare (manager)
2022-10-21 09:55

 Now that bug 0000249 has been resolved, this bug can be revisited.

- Issue History
Date Modified Username Field Change
2020-10-24 22:01 philip-guenther New Issue
2020-10-24 22:01 philip-guenther Name => Philip Guenther
2020-10-24 22:01 philip-guenther Organization => OpenBSD
2020-10-24 22:01 philip-guenther Section => printf's APPLICATION USAGE
2020-10-24 22:01 philip-guenther Page Number => 3038
2020-10-24 22:01 philip-guenther Line Number => 102845 - 102848
2021-02-18 17:11 nick Relationship added child of 0000249
2021-02-18 17:12 nick Note Added: 0005248
2021-02-18 17:13 nick Status New => Resolution Proposed
2021-02-18 17:13 nick Resolution Open => Accepted As Marked
2021-02-18 17:14 nick Final Accepted Text => See Note: 0005248
2021-02-18 17:15 nick Tag Attached: issue8
2021-03-15 20:53 mirabilos Note Added: 0005274
2021-03-16 10:01 geoffclare Note Added: 0005276
2022-10-21 09:55 geoffclare Note Added: 0006011
2022-10-21 09:55 geoffclare Status Resolution Proposed => Under Review
2022-10-21 10:03 geoffclare Resolution Accepted As Marked => Reopened
2022-11-03 15:24 geoffclare Final Accepted Text See Note: 0005248 => See Note: 0005276
2022-11-03 15:24 geoffclare Status Under Review => Resolved
2022-11-03 15:24 geoffclare Resolution Reopened => Accepted As Marked
2022-11-30 16:46 geoffclare Status Resolved => Applied
2024-06-11 09:12 agadmin Status Applied => Closed

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