Thread: BUFSIZ value

  1. #1
    Registered User
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    Jun 2004

    BUFSIZ value

    I noticed that the BUFSIZ macro in stdio.h contains different values for different compilers for the same platform (windows).

    gcc uses 1024
    VS6 512 or 4096
    some older borland compiler i saw used 2048

    Anybody knows why this is different each time? Shouldnt there be one value which fits best for a certain platform?

  2. #2
    ATH0 quzah's Avatar
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    Oct 2001
    The C standard specifies the minimum size. You're allowed to have it larger than that.

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  3. #3
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    Dec 2005
    There is no Specific reason behind different values of BUFSIZE from C standard side. Its depends on the compiler developer that what size he find suitable.
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  4. #4
    Frequently Quite Prolix dwks's Avatar
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    Apr 2005
    Macro: int BUFSIZ
    The value of this macro is an integer constant expression that is good to use for the size argument to setvbuf. This value is guaranteed to be at least 256.

    The value of BUFSIZ is chosen on each system so as to make stream I/O efficient. So it is a good idea to use BUFSIZ as the size for the buffer when you call setvbuf.

    Actually, you can get an even better value to use for the buffer size by means of the fstat system call: it is found in the st_blksize field of the file attributes. See section 14.9.1 The meaning of the File Attributes.

    Sometimes people also use BUFSIZ as the allocation size of buffers used for related purposes, such as strings used to receive a line of input with fgets (see section 12.8 Character Input). There is no particular reason to use BUFSIZ for this instead of any other integer, except that it might lead to doing I/O in chunks of an efficient size.

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  5. #5
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    Mar 2006
    Different compilers may compile the same code differently, even on the same platform. (Try it: compare gcc/vc/icc generated asm side by side, and maybe repeat with optimization switches.)
    #include <stdio.h>
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

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