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* doc/posix-functions/realloc.texi (realloc): Mention pitfalls of passing 0 size to realloc. Signed-off-by: Eric Blake <eblake@redhat.com>
36 lines
1.3 KiB
Plaintext
36 lines
1.3 KiB
Plaintext
@node realloc
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@section @code{realloc}
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@findex realloc
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POSIX specification:@* @url{http://www.opengroup.org/onlinepubs/9699919799/functions/realloc.html}
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Gnulib module: realloc-posix
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Portability problems fixed by Gnulib:
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@itemize
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@item
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Upon failure, the function does not set @code{errno} to @code{ENOMEM} on
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some platforms:
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mingw.
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@end itemize
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Portability problems not fixed by Gnulib:
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@itemize
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@item
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It is not portable to call @code{realloc} with a size of 0. With a
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NULL pointer argument, this is the same ambiguity as @code{malloc (0)}
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on whether a unique zero-size object is created. With a non-NULL
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pointer argument, C99 requires that if @code{realloc (p, 0)} returns
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@code{NULL} then @code{p} is still valid. Among implementations that
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obey C99, behavior varies on whether @code{realloc (p, 0)} always
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fails and leaves @code{p} valid, or usually succeeds and returns a
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unique zero-size object; either way, a program not suspecting these
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semantics will leak memory (either the still-valid @code{p}, or the
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non-NULL return value). Meanwhile, several implementations violate
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C99, by always calling @code{free (p)} but returning NULL:
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glibc, Cygwin
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@end itemize
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Extension: Gnulib provides a module @samp{realloc-gnu} that substitutes a
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@code{realloc} implementation that behaves more like the glibc implementation.
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