diff options
| author | Martin Sebor <msebor@redhat.com> | 2018-06-29 10:45:19 -0600 |
|---|---|---|
| committer | Martin Sebor <msebor@redhat.com> | 2018-06-29 10:45:19 -0600 |
| commit | 7e8989d03b5b3eea4f4225445c60413d36f2d710 (patch) | |
| tree | 5baffad1e52fdd343b6b193e2e1887be15669e77 | |
| parent | bac15a72fcf0ed143dd959604d9317c4bb94160a (diff) | |
Document interaction with GCC built-ins in the Customizing Printf
section of the manual.
| -rw-r--r-- | ChangeLog | 5 | ||||
| -rw-r--r-- | manual/stdio.texi | 16 |
2 files changed, 17 insertions, 4 deletions
@@ -1,3 +1,8 @@ +2018-06-29 Martin Sebor <msebor@redhat.com> + + * manual/stdio.texi (Customizing Printf): Mention interaction + with GCC built-ins. + 2018-06-29 Maciej W. Rozycki <macro@mips.com> [BZ #23307] diff --git a/manual/stdio.texi b/manual/stdio.texi index 379f003b3f..bbd3061bab 100644 --- a/manual/stdio.texi +++ b/manual/stdio.texi @@ -2962,7 +2962,11 @@ The facilities of this section are declared in the header file @strong{Portability Note:} The ability to extend the syntax of @code{printf} template strings is a GNU extension. ISO standard C has -nothing similar. +nothing similar. When using the GNU C compiler or any other compiler +that interprets calls to standard I/O functions according to the rules +of the language standard it is necessary to disable such handling by +the appropriate compiler option. Otherwise the behavior of a program +that relies on the extension is undefined. @node Registering New Conversions @subsection Registering New Conversions @@ -3016,9 +3020,13 @@ function when this format specifier appears in the format string. The return value is @code{0} on success, and @code{-1} on failure (which occurs if @var{spec} is out of range). -You can redefine the standard output conversions, but this is probably -not a good idea because of the potential for confusion. Library routines -written by other people could break if you do this. +@strong{Portability Note:} It is possible to redefine the standard output +conversions but doing so is strongly discouraged because it may interfere +with the behavior of programs and compiler implementations that assume +the effects of the conversions conform to the relevant language standards. +In addition, conforming compilers need not guarantee that the function +registered for a standard conversion will be called for each such +conversion in every format string in a program. @end deftypefun @node Conversion Specifier Options |