[ http://issues.apache.org/jira/browse/STDCXX-7?page=all ]

Martin Sebor updated STDCXX-7:
------------------------------

    Fix Version: 4.2
                     (was: 4.1.4)

> std::operator<<(ostream&, const char*) inefficient for unbuffered file I/O
> --------------------------------------------------------------------------
>
>          Key: STDCXX-7
>          URL: http://issues.apache.org/jira/browse/STDCXX-7
>      Project: C++ Standard Library
>         Type: Bug

>   Components: 27. Input/Output
>     Versions: 4.1.2
>  Environment: All.
>     Reporter: Martin Sebor
>      Fix For: 4.2

>
> operator<<(ostream&, const char*) is inefficient when the stream argument is an unbuffered fstream object: it causes a call to write() for each character  (ditto for the wide character versions). This affects all platforms. Here's a test case with HP aCC:
> $ cat t.cpp && nice gmake SRCS=t.cpp && truss -o truss.out ./t && grep write truss.out
> #include <fstream>
> int main ()
> {
>     std::ofstream f ("/dev/tty");
>     f.rdbuf ()->pubsetbuf (0, 0);
>     f << "abcdef\n";
> }
> aCC -c -I/build/sebor/dev/stdlib/include/ansi -I/usr/include  -D_RWSTDDEBUG   -mt -D_RWSTD_USE_CONFIG -I/build/sebor/aCC-3.63-15s/include -I/build/sebor/dev/stdlib/include -I/build/sebor/dev/stdlib/examples/include  -Aa +nostl  -g +d  +w +W392 +W655 +W684 +W818 +W819 +W849  t.cpp 
> aCC t.o -o t -Aa +nostl -Wl,+s -Wl,+vnocompatwarnings -L/build/sebor/aCC-3.63-15s/lib   -mt  -L/build/sebor/aCC-3.63-15s/lib -lstd15s  -lm  
> abcdef
> write(4, "a ", 1)                                          = 1
> write(4, "b ", 1)                                          = 1
> write(4, "c ", 1)                                          = 1
> write(4, "d ", 1)                                          = 1
> write(4, "e ", 1)                                          = 1
> write(4, "f ", 1)                                          = 1
> write(4, "\n", 1)                                          = 1

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