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-rw-r--r--manual/stdio.texi87
1 files changed, 82 insertions, 5 deletions
diff --git a/manual/stdio.texi b/manual/stdio.texi
index 8517653..83f4f92 100644
--- a/manual/stdio.texi
+++ b/manual/stdio.texi
@@ -330,6 +330,14 @@ this ability, so using @code{freopen} is more portable.
When the sources are compiled with @code{_FILE_OFFSET_BITS == 64} on a
32 bit machine this function is in fact @code{freopen64} since the LFS
interface replaces transparently the old interface.
+
+@Theglibc{} only supports use of @code{freopen} on streams opened with
+@code{fopen} or @code{fopen64} and on the original values of the
+standard streams @code{stdin}, @code{stdout}, and @code{stderr}; such
+a stream may be reopened multiple times with @code{freopen}. If it is
+called on another kind of stream (opened with functions such as
+@code{popen}, @code{fmemopen}, @code{open_memstream}, and
+@code{fopencookie}), @code{freopen} fails and returns a null pointer.
@end deftypefun
@deftypefun {FILE *} freopen64 (const char *@var{filename}, const char *@var{opentype}, FILE *@var{stream})
@@ -921,6 +929,9 @@ Therefore, @var{stream} should never be an expression with side-effects.
@safety{@prelim{}@mtsafe{@mtsrace{:stream}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
The @code{putc_unlocked} function is equivalent to the @code{putc}
function except that it does not implicitly lock the stream.
+Like @code{putc}, it may be implemented as a macro and may evaluate
+the @var{stream} argument more than once. Therefore, @var{stream}
+should not be an expression with side-effects.
@end deftypefun
@deftypefun wint_t putwc_unlocked (wchar_t @var{wc}, FILE *@var{stream})
@@ -1124,6 +1135,9 @@ Therefore, @var{stream} should never be an expression with side-effects.
@safety{@prelim{}@mtsafe{@mtsrace{:stream}}@asunsafe{@asucorrupt{}}@acunsafe{@acucorrupt{}}}
The @code{getc_unlocked} function is equivalent to the @code{getc}
function except that it does not implicitly lock the stream.
+Like @code{getc}, it may be implemented as a macro and may evaluate
+the @var{stream} argument more than once. Therefore, @var{stream}
+should not be an expression with side-effects.
@end deftypefun
@deftypefun wint_t getwc_unlocked (FILE *@var{stream})
@@ -1467,11 +1481,9 @@ program; usually @code{ungetc} is used only to unread a character that
was just read from the same stream. @Theglibc{} supports this
even on files opened in binary mode, but other systems might not.
-@Theglibc{} only supports one character of pushback---in other
-words, it does not work to call @code{ungetc} twice without doing input
-in between. Other systems might let you push back multiple characters;
-then reading from the stream retrieves the characters in the reverse
-order that they were pushed.
+@Theglibc{} supports pushing back multiple characters; subsequently
+reading from the stream retrieves the characters in the reverse order
+that they were pushed.
Pushing back characters doesn't alter the file; only the internal
buffering for the stream is affected. If a file positioning function
@@ -1565,6 +1577,9 @@ The @code{fread_unlocked} function is equivalent to the @code{fread}
function except that it does not implicitly lock the stream.
This function is a GNU extension.
+This function may be implemented as a macro and may evaluate
+@var{stream} more than once. Therefore, @var{stream} should not be an
+expression with side-effects.
@end deftypefun
@deftypefun size_t fwrite (const void *@var{data}, size_t @var{size}, size_t @var{count}, FILE *@var{stream})
@@ -1583,6 +1598,9 @@ The @code{fwrite_unlocked} function is equivalent to the @code{fwrite}
function except that it does not implicitly lock the stream.
This function is a GNU extension.
+This function may be implemented as a macro and may evaluate
+@var{stream} more than once. Therefore, @var{stream} should not be an
+expression with side-effects.
@end deftypefun
@node Formatted Output
@@ -2356,6 +2374,29 @@ the easiest way to make sure you have all the right prototypes is to
just include @file{stdio.h}.
@pindex stdio.h
+The @code{printf} family shares the error codes listed below.
+Individual functions may report additional @code{errno} values if they
+fail.
+
+@table @code
+@item EOVERFLOW
+The number of written bytes would have exceeded @code{INT_MAX}, and thus
+could not be represented in the return type @code{int}.
+
+@item ENOMEM
+The function could not allocate memory during processing. Long argument
+lists and certain floating point conversions may require memory
+allocation, as does initialization of an output stream upon first use.
+
+@item EILSEQ
+POSIX specifies this error code should be used if a wide character is
+encountered that does not have a matching valid character. @Theglibc{}
+always performs transliteration, using a replacement character if
+necessary, so this error condition cannot occur on output. However,
+@theglibc{} uses @code{EILSEQ} to indicate that an input character
+sequence (wide or multi-byte) could not be converted successfully.
+@end table
+
@deftypefun int printf (const char *@var{template}, @dots{})
@standards{ISO, stdio.h}
@safety{@prelim{}@mtsafe{@mtslocale{}}@asunsafe{@asucorrupt{} @ascuheap{}}@acunsafe{@acsmem{} @aculock{} @acucorrupt{}}}
@@ -2502,6 +2543,26 @@ store the result in which case @code{-1} is returned. This was
changed in order to comply with the @w{ISO C99} standard.
@end deftypefun
+@deftypefun int dprintf (int @var{fd}, @var{template}, ...)
+@standards{POSIX, stdio.h}
+@safety{@mtsafe{@mtslocale{}}@asunsafe{@ascuheap{}}@acunsafe{@acsmem{}}}
+This function formats its arguments according to @var{template} and
+writes the result to the file descriptor @var{fd}, using the
+@code{write} function. It returns the number of bytes written, or a
+negative value if there was an error. In the error case, @code{errno}
+is set appropriately. The possible @code{errno} values depend on the
+type of the file descriptor @var{fd}, in addition to the general
+@code{printf} error codes.
+
+The number of calls to @code{write} is unspecified, and some @code{write}
+calls may have happened even if @code{dprintf} returns with an error.
+
+@strong{Portability Note:} POSIX does not require that this function is
+async-signal-safe, and @theglibc{} implementation is not. However, some
+other systems offer this function as an async-signal-safe alternative to
+@code{fprintf}. @xref{POSIX Safety Concepts}.
+@end deftypefun
+
@node Dynamic Output
@subsection Dynamically Allocating Formatted Output
@@ -2715,6 +2776,13 @@ The @code{obstack_vprintf} function is the equivalent of
as for @code{vprintf}.
@end deftypefun
+@deftypefun int vdprintf (int @var{fd}, const char *@var{template}, va_list @var{ap})
+@standards{POSIX, stdio.h}
+@safety{@mtsafe{@mtslocale{}}@asunsafe{@ascuheap{}}@acunsafe{@acsmem{}}}
+The @code{vdprintf} is the equivalent of @code{dprintf}, but processes
+an argument list.
+@end deftypefun
+
Here's an example showing how you might use @code{vfprintf}. This is a
function that prints error messages to the stream @code{stderr}, along
with a prefix indicating the name of the program
@@ -4112,6 +4180,15 @@ check indicators that are part of the internal state of the stream
object, indicators set if the appropriate condition was detected by a
previous I/O operation on that stream.
+The end of file and error conditions are mutually exclusive. For a
+narrow oriented stream, end of file is not considered an error. For
+wide oriented streams, reaching the end of the underlying file can
+result an error if the underlying file ends with an incomplete multibyte
+sequence. This is reported as an error by @code{ferror}, and not as an
+end of file by @code{feof}. End of file on wide oriented streams that
+does not fall into the middle of a multibyte sequence is reported via
+@code{feof}.
+
@deftypevr Macro int EOF
@standards{ISO, stdio.h}
This macro is an integer value that is returned by a number of narrow