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Posted to dev@stdcxx.apache.org by "Martin Sebor (JIRA)" <ji...@apache.org> on 2006/12/11 21:53:21 UTC
[jira] Resolved: (STDCXX-7) std::operator<<(ostream&, const char*)
inefficient for unbuffered file I/O
[ http://issues.apache.org/jira/browse/STDCXX-7?page=all ]
Martin Sebor resolved STDCXX-7.
-------------------------------
Resolution: Fixed
Running the program after applying the referenced patch shows just a single call to write(1):
$ truss -t write ./t
abcdef
write(3, " a b c d e f\n", 7) = 7
> 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
> Issue Type: Bug
> Components: 27. Input/Output
> Affects Versions: 4.1.2
> Environment: All.
> Reporter: Martin Sebor
> Assigned To: 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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