From 554fd8c5195424bdbcabf5de30fdc183aba391bd Mon Sep 17 00:00:00 2001 From: upstream source tree Date: Sun, 15 Mar 2015 20:14:05 -0400 Subject: obtained gcc-4.6.4.tar.bz2 from upstream website; verified gcc-4.6.4.tar.bz2.sig; imported gcc-4.6.4 source tree from verified upstream tarball. downloading a git-generated archive based on the 'upstream' tag should provide you with a source tree that is binary identical to the one extracted from the above tarball. if you have obtained the source via the command 'git clone', however, do note that line-endings of files in your working directory might differ from line-endings of the respective files in the upstream repository. --- libstdc++-v3/doc/html/manual/io_and_c.html | 57 ++++++++++++++++++++++++++++++ 1 file changed, 57 insertions(+) create mode 100644 libstdc++-v3/doc/html/manual/io_and_c.html (limited to 'libstdc++-v3/doc/html/manual/io_and_c.html') diff --git a/libstdc++-v3/doc/html/manual/io_and_c.html b/libstdc++-v3/doc/html/manual/io_and_c.html new file mode 100644 index 000000000..6b4066154 --- /dev/null +++ b/libstdc++-v3/doc/html/manual/io_and_c.html @@ -0,0 +1,57 @@ + + +Interacting with C
Interacting with C
Prev Chapter 13.  + Input and Output + + Next

Interacting with C

+ See the extensions for using + FILE and file descriptors with + ofstream and + ifstream. +

+ Pathetic Performance? Ditch C. +

It sounds like a flame on C, but it isn't. Really. Calm down. + I'm just saying it to get your attention. +

Because the C++ library includes the C library, both C-style and + C++-style I/O have to work at the same time. For example: + 

+     #include <iostream>
+     #include <cstdio>
+
+     std::cout << "Hel";
+     std::printf ("lo, worl");
+     std::cout << "d!\n";
+

This must do what you think it does. +

Alert members of the audience will immediately notice that buffering + is going to make a hash of the output unless special steps are taken. +

The special steps taken by libstdc++, at least for version 3.0, + involve doing very little buffering for the standard streams, leaving + most of the buffering to the underlying C library. (This kind of + thing is tricky to get right.) + The upside is that correctness is ensured. The downside is that + writing through cout can quite easily lead to awful + performance when the C++ I/O library is layered on top of the C I/O + library (as it is for 3.0 by default). Some patches have been applied + which improve the situation for 3.1. +

However, the C and C++ standard streams only need to be kept in sync + when both libraries' facilities are in use. If your program only uses + C++ I/O, then there's no need to sync with the C streams. The right + thing to do in this case is to call + 

+     #include any of the I/O headers such as ios, iostream, etc
+
+     std::ios::sync_with_stdio(false);
+

You must do this before performing any I/O via the C++ stream objects. + Once you call this, the C++ streams will operate independently of the + (unused) C streams. For GCC 3.x, this means that cout and + company will become fully buffered on their own. +

Note, by the way, that the synchronization requirement only applies to + the standard streams (cin, cout, + cerr, + clog, and their wide-character counterchapters). File stream + objects that you declare yourself have no such requirement and are fully + buffered. +

Prev Up Next
File Based Streams Home Chapter 14.  + Atomics + +
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