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51 lines
2.4 KiB
51 lines
2.4 KiB
1 month ago
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commit 10de4a47ef3f481592e3c62eb07bcda23e9fde4d
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Author: Arjun Shankar <arjun@redhat.com>
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Date: Mon Jul 29 14:30:59 2024 +0200
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manual/stdio: Clarify putc and putwc
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The manual entry for `putc' described what "most systems" do instead of
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describing the glibc implementation and its guarantees. This commit
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fixes that by warning that putc may be implemented as a macro that
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double-evaluates `stream', and removing the performance claim.
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Even though the current `putc' implementation does not double-evaluate
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`stream', offering this obscure guarantee as an extension to what
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POSIX allows does not seem very useful.
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The entry for `putwc' is also edited to bring it in line with `putc'.
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Reviewed-by: Florian Weimer <fweimer@redhat.com>
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diff --git a/manual/stdio.texi b/manual/stdio.texi
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index fd7ed0cedc7c1a59..0c9a7ce4a9df4c05 100644
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--- a/manual/stdio.texi
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+++ b/manual/stdio.texi
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@@ -903,21 +903,21 @@ This function is a GNU extension.
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@deftypefun int putc (int @var{c}, FILE *@var{stream})
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@standards{ISO, stdio.h}
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@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{} @aculock{}}}
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-This is just like @code{fputc}, except that most systems implement it as
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+This is just like @code{fputc}, except that it may be implemented as
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a macro, making it faster. One consequence is that it may evaluate the
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@var{stream} argument more than once, which is an exception to the
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-general rule for macros. @code{putc} is usually the best function to
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-use for writing a single character.
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+general rule for macros. Therefore, @var{stream} should never be an
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+expression with side-effects.
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@end deftypefun
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@deftypefun wint_t putwc (wchar_t @var{wc}, FILE *@var{stream})
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@standards{ISO, wchar.h}
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@safety{@prelim{}@mtsafe{}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{} @aculock{}}}
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-This is just like @code{fputwc}, except that it can be implement as
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+This is just like @code{fputwc}, except that it may be implemented as
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a macro, making it faster. One consequence is that it may evaluate the
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@var{stream} argument more than once, which is an exception to the
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-general rule for macros. @code{putwc} is usually the best function to
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-use for writing a single wide character.
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+general rule for macros. Therefore, @var{stream} should never be an
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+expression with side-effects.
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@end deftypefun
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@deftypefun int putc_unlocked (int @var{c}, FILE *@var{stream})
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