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How can I tell how much destination buffer space ...
How can I tell how much destination buffer space I'll need for an arbitrary sprintf call? How can I avoid overflowing the destination buffer with sprintf? When the format string being used with sprintf is known and relatively simple, you can sometimes predict a buffer size in an ad-hoc way. If the f... 2015-10-19, 1864👍, 0💬

Are pointers really faster than arrays?
Are pointers really faster than arrays? How much do function calls slow things down? Is ++i faster than i = i + 1? Precise answers to these and many similar questions depend of course on the processor and compiler in use. If you simply must know, you'll have to time test programs carefully. (Often t... 2015-02-09, 1860👍, 0💬

Why does the declaration extern int .....
Why does the declaration extern int f(struct x *p); give me an obscure warning message about ``struct x declared inside parameter list''? In a quirk of C's normal block scoping rules, a structure declared (or even mentioned) for the first time within a prototype cannot be compatible with other struc... 2016-01-11, 1857👍, 0💬

What is the ANSI C Standard?
What is the ANSI C Standard? In 1983, the American National Standards Institute (ANSI) commissioned a committee, X3J11, to standardize the C language. After a long, arduous process, including several widespread public reviews, the committee's work was finally ratified as ANS X3.159-1989 on December ... 2016-01-15, 1854👍, 0💬

How can I call FORTRAN?
How can I call FORTRAN? Q: How can I call FORTRAN (C++, BASIC, Pascal, Ada, LISP) functions from C? (And vice versa?) A: The answer is entirely dependent on the machine and the specific calling sequences of the various compilers in use, and may not be possible at all. Read your compiler documentatio... 2015-01-12, 1854👍, 0💬

Since array references decay into pointers ...
Since array references decay into pointers, if arr is an array, what's the difference between arr and &arr? The type. In Standard C, &arr yields a pointer, of type pointer-to-array-of-T, to the entire array. (In pre-ANSI C, the & in &arr generally elicited a warning, and was generall... 2015-12-09, 1853👍, 0💬

How can I include expansions of the macros .....
How can I include expansions of the __FILE__ and __LINE__ macros in a general-purpose debugging macro? One solution involves writing your debug macro in terms of a varargs function , and an auxiliary function which stashes the values of __FILE__ and __LINE__ away in static variables, as in: #include... 2016-01-15, 1850👍, 0💬

I am trying to sort an array of strings with qsort, using strcmp as the comparison function, but it is not working.
I am trying to sort an array of strings with qsort, using strcmp as the comparison function, but it is not working. By ``array of strings'' you probably mean ``array of pointers to char.'' The arguments to qsort's comparison function are pointers to the objects being sorted, in this case, pointers t... 2015-08-12, 1850👍, 0💬

How can I list all of the predefined identifiers?
How can I list all of the predefined identifiers? There's no standard way, although it is a common need. gcc provides a -dM option which works with -E, and other compilers may provide something similar. If the compiler documentation is unhelpful, the most expedient way is probably to extract printab... 2016-01-27, 1845👍, 0💬

Is exit status truly equivalent to returning the same status from main?
Is exit status truly equivalent to returning the same status from main? Yes and no. The Standard says that a return from the initial call to main is equivalent to calling exit. However, a return from main cannot be expected to work if data local to main might be needed during cleanup;A few very old,... 2015-12-16, 1845👍, 0💬

What printf format should I use for a typedef like size_t when I don't know whether it is long or some other type?
What printf format should I use for a typedef like size_t when I don't know whether it is long or some other type? Use a cast to convert the value to a known, conservatively-sized type, then use the printf format matching that type. For example, to print the size of a type, you might use printf("%lu... 2015-11-04, 1845👍, 0💬

How can I convert integers to binary or hexadecimal?
How can I convert integers to binary or hexadecimal? Make sure you really know what you're asking. Integers are stored internally in binary, although for most purposes it is not incorrect to think of them as being in octal, decimal, or hexadecimal, whichever is convenient. The base in which a number... 2015-02-13, 1842👍, 0💬

I believe that declaring void main) cant fail ...
I believe that declaring void main() can't fail, since I'm calling exit instead of returning, and anyway my operating system ignores a program's exit/return status. It doesn't matter whether main returns or not, or whether anyone looks at the status; the problem is that when main is misdeclared, its... 2015-12-18, 1840👍, 0💬

What is the difference between memcpy and memmove?
What is the difference between memcpy and memmove? memmove offers guaranteed behavior if the memory regions pointed to by the source and destination arguments overlap. memcpy makes no such guarantee, and may therefore be more efficiently implementable. When in doubt, it's safer to use memmove. It se... 2015-12-07, 1838👍, 0💬

If you cant modify string literals, why arent they defined as being arrays of const characters?
If you cant modify string literals, why arent they defined as being arrays of const characters? One reason is that so very much code contains lines like char *p = "Hello, world!"; which are not necessarily incorrect. These lines would suffer the diagnostic messages, but it's really any later attempt... 2016-01-06, 1837👍, 0💬

I am using header files which accompany two different third-party libraries...
I'm using header files which accompany two different third-party libraries, and they are ``helpfully'' defining common macros such as TRUE, FALSE, Min(), and Max(), but the definitions clash with each other and with definitions I'd already established in my own header files. What can I do? This is i... 2016-02-10, 1836👍, 0💬

Now I am trying to sort an array of structures with qsort ...
Now I'm trying to sort an array of structures with qsort. My comparison function takes pointers to structures, but the compiler complains that the function is of the wrong type for qsort. How can I cast the function pointer to shut off the warning? The conversions must be in the comparison function,... 2015-08-10, 1836👍, 0💬

Wy compiler is rejecting the simplest possible test programs ...
My compiler is rejecting the simplest possible test programs, with all kinds of syntax errors. It's complaining about the first line of main(int argc, char **argv) { return 0; } Perhaps it is a pre-ANSI compiler, unable to accept function prototypes and the like. If you don't have access to an ANSI ... 2015-12-02, 1832👍, 0💬

What is C language?
What is C language? The C programming language is a standardized programming language developed in the early 1970s by Ken Thompson and Dennis Ritchie for use on the UNIX operating system. It has since spread to many other operating systems, and is one of the most widely used programming languages. C... 2014-12-31, 1830👍, 0💬

How can I manipulate individual bits??
How can I manipulate individual bits?? Bit manipulation is straightforward in C, and commonly done. To extract (test) a bit, use the bitwise AND (&amp;) operator, along with a bit mask representing the bit(s) you're interested in: value &amp; 0x04 To set a bit, use the bitwise OR (| or |=) o... 2015-02-20, 1827👍, 0💬

So can I query the malloc package to find out how big an allocated block is?
So can I query the malloc package to find out how big an allocated block is? Unfortunately, there is no standard or portable way. (Some compilers provide nonstandard extensions.) If you need to know, you'll have to keep track of it yourself. 2016-03-24, 1826👍, 0💬

I cant get strcat to work. I tried ...
I can't get strcat to work. I tried char *s1 = "Hello, ";br> char *s2 = "world!";br> char *s3 = strcat(s1, s2);br> but I got strange results. the main problem here is that space for the concatenated result is not properly allocated. C does not provide an automatically-managed string type. C compiler... 2016-03-09, 1822👍, 0💬

What does pragma once mean? I found it in some header files.
What does pragma once mean? I found it in some header files. It is an extension implemented by some preprocessors to help make header files idempotent; that is, to make sure that their contents are processed exactly once even if they are #included multiple times.Some people claim that #pragma once c... 2015-12-11, 1820👍, 0💬

Here is a good puzzle: how do you write a program which produces its own source code as output?
Here is a good puzzle: how do you write a program which produces its own source code as output? It is actually quite difficult to write a self-reproducing program that is truly portable, due particularly to quoting and character set difficulties. Here is a classic example (which ought to be presente... 2015-01-02, 1820👍, 0💬

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.NET C C++ CSS DBA General HTML Java JavaScript JSP JUnit MySQL Networking Oracle Perl Perl PHP PL/SQL RSS Software QA SQL Server Struts Unix Windows XHTML XML