C++博客-Apollo Fang's Blog-随笔分类-Miscellaneous

VI十六进制模式正常模式切换

Apollo Fang — Wed, 31 Oct 2012 09:16:00 GMT

VIM显示十六进制的方法- %!xxd
VIM回复正常显示方法- %!xxd -r

Apollo Fang 2012-10-31 17:16 发表评论

What is "##" string in C code

Apollo Fang — Fri, 08 Jun 2012 02:42:00 GMT

See code below(quoting ffmpeg source code)

1 #define REGISTER_MUXER(X,x) { \
2     extern AVOutputFormat x##_muxer; \
3     if(CONFIG_##X##_MUXER) av_register_output_format(&x##_muxer); }
4 #define REGISTER_DEMUXER(X,x) { \
5 extern AVInputFormat x##_demuxer; \
6     if(CONFIG_##X##_DEMUXER) av_register_input_format(&x##_demuxer); }
7 #define REGISTER_MUXDEMUX(X,x)  REGISTER_MUXER(X,x); REGISTER_DEMUXER(X,x)
8 #define REGISTER_PROTOCOL(X,x) { \
9     extern URLProtocol x##_protocol; \
10     if(CONFIG_##X##_PROTOCOL) av_register_protocol2(&x##_protocol, sizeof(x##_protocol)); }

"##" string in C language code is used for concatenating the two strings which is before and behind it in a macros definition.
See a test code below :

1 #define DEFINE(t, x)  {t x##_##t;}
3 int main()
4 {
5     DEFINE(int, vvv);
6     return 0;
7 }

Use "gcc -E test_sharpsharp.c -o test_sharpsharp.i" command to pre-process this file
And the output file "test_sharpsharp.i" just looks like below :

1 int main()
2 {
3 {int vvv_int;};
4 return 0;
5 }

The code below is useful, and you can use "##" macro definitions to realize sample templates with C language

1 #define REGISTER_DATA_COMPARE(x)\
2     static __inline x x##_compare(x key1, x key2)\
3     {\
4         if (key1 > key2) return 1;\
5         if (key1 < key2) return -1;\
6   return 0;\
7     }

In this way, you can realize a data comparing function set, when you need comparing some type of data, just register it.

Apollo Fang 2012-06-08 10:42 发表评论

How to update or install pthread manual reference on Linux

Apollo Fang — Thu, 27 Oct 2011 05:28:00 GMT

If you want to install the manual reference about pthread, execute the following command:

sudo apt-get install glibc-doc
sudo apt-get install manpages-posix-dev

Apollo Fang 2011-10-27 13:28 发表评论

How To Disable "_CRT_SECURE_NO_WARNINGS" Warnings

Apollo Fang — Tue, 25 Oct 2011 09:26:00 GMT

While you using MS Visual Studio, there are always "_CRT_SECURE_NO_WARNINGS" warnings appeared, like bellow:

"warning C4996: 'strerror': This function or variable may be unsafe. Using strerror_s instead."

How to disable this kind deprecation? Do like bellow (VS2010):

Project -> Properties -> Configuration Properties -> C++ -> Processor -> Processor Definitions

And then add a macro definition "_CRT_SECURE_NO_WARNINGS", and use a ";" to separated with others

OK, Hit OK and enjoy the silence...

Tuesday, October 25, 2011

Apollo Fang 2011-10-25 17:26 发表评论