.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

<< < 1 2 3 4 5 6 7 8 9 10 … > >>   Sort: Date

y program is crashing, apparently somewhere down inside malloc ....
My program is crashing, apparently somewhere down inside malloc, but I can't see anything wrong with it. Is there a bug in malloc? It is unfortunately very easy to corrupt malloc's internal data structures, and the resulting problems can be stubborn. The most common source of problems is writing mor... 2016-04-06, 2073👍, 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... 2015-07-16, 2073👍, 0💬

How can I read one character at a time, without waiting for the RETURN key
How can I read one character at a time, without waiting for the RETURN key Alas, there is no standard or portable way to do these things in C. Concepts such as screens and keyboards are not even mentioned in the Standard, which deals only with simple I/O ``streams'' of characters. Input to a compute... 2015-11-11, 2070👍, 0💬

What is the difference between calloc and malloc? ....
What's the difference between calloc and malloc? Which should I use? Is it safe to take advantage of calloc's zero-filling? Does free work on memory allocated with calloc, or do you need a cfree? calloc(m, n) is essentially equivalent to p = malloc(m * n); memset(p, 0, m * n); There is no important ... 2016-03-16, 2068👍, 0💬

Why doesnt this code work?
Why doesn't this code: double d; scanf("%f", &amp;d); work? Unlike printf, scanf uses %lf for values of type double, and %f for float.%f tells scanf to expect a pointer-to-float, not the pointer-to-double you gave it. Either use %lf, or declare the receiving variable as a float. 2015-10-30, 2055👍, 0💬

How can I handle floating-point exceptions gracefully?
How can I handle floating-point exceptions gracefully? On many systems, you can define a function matherr which will be called when there are certain floating-point errors, such as errors in the math routines in . You may also be able to use signal to catch SIGFPE. 2015-06-21, 2052👍, 0💬

Why doesn't C have an exponentiation operator?
Why doesn't C have an exponentiation operator? One reason is probably that few processors have a built-in exponentiation instruction. C has a pow function (declared in &lt;math.h>) for performing exponentiation, although explicit multiplication is usually better for small positive integral expon... 2015-06-24, 2051👍, 0💬

Why cant I pass a char to a function which expects a const char ?
Why cant I pass a char to a function which expects a const char ? You can use a pointer-to-T (for any type T) where a pointer-to-const-T is expected. However, the rule (an explicit exception) which permits slight mismatches in qualified pointer types is not applied recursively, but only at the top l... 2016-01-04, 2048👍, 0💬

What is the best way of making my program efficient?
What is the best way of making my program efficient? By picking good algorithms, implementing them carefully, and making sure that your program isn't doing any extra work. For example, the most microoptimized character-copying loop in the world will be beat by code which avoids having to copy charac... 2015-02-11, 2046👍, 0💬

Can I declare main as void, to shut off these annoying ....
Can I declare main as void, to shut off these annoying ``main returns no value'' messages? No. main must be declared as returning an int, and as taking either zero or two arguments, of the appropriate types. If you're calling exit() but still getting warnings, you may have to insert a redundant retu... 2015-12-20, 2038👍, 0💬

How do I swap bytes?
How do I swap bytes? V7 Unix had a swab function, but it seems to have been forgotten. A problem with explicit byte-swapping code is that you have to decide whether to call it or not, based on the byte order of the data and the byte order of the machine in use. A better solution is to define functio... 2015-02-16, 2034👍, 0💬

I im dynamically allocating an array, like this ...
I'm dynamically allocating an array, like this: int *iarray = (int *)malloc(nints); malloc isn't returning NULL, but the code isn't working. A:malloc is a low-level, typeless allocator. It doesn't know how you're going to use the memory; all it does is to allocate as many bytes of memory as you ask ... 2016-04-06, 2033👍, 0💬

How can I split up a string into whitespace-separated fields?
How can I split up a string into whitespace-separated fields? How can I duplicate the process by which main() is handed argc and argv? The only Standard function available for this kind of ``tokenizing'' is strtok, although it can be tricky to use and it may not do everything you want it to. (For in... 2015-08-17, 2019👍, 0💬

I have seen function declarations that look like this
I've seen function declarations that look like this: extern int func __((int, int)); What are those extra parentheses and underscores for? They're part of a trick which allows the prototype part of the function declaration to be turned off for a pre-ANSI compiler. Somewhere else is a conditional def... 2015-05-23, 2018👍, 0💬

What is the right type to use for Boolean values in C? ....
What is the right type to use for Boolean values in C? Is there a standard type? Should I use #defines or enums for the true and false values? Traditionally, C did not provide a standard Boolean type, partly and partly to allow the programmer to make the appropriate space/time tradeoff. (Using an in... 2016-03-02, 2017👍, 0💬

Why doesnt long int work?
Why doesn't long int n = 123456; printf("%d\n", n); work? Whenever you print long ints you must use the l (lower case letter ``ell'') modifier in the printf format (e.g. %ld). printf can't know the types of the arguments which you've passed to it, so you must let it know by using the correct format ... 2015-11-09, 2013👍, 0💬

How can I get the numeric value corresponding to a character? ....
How can I get the numeric value (i.e. ASCII or other character set code) corresponding to a character, or vice versa? In C, characters are represented by small integers corresponding to their values in the machine's character set. Therefore, you don't need a conversion function: if you have the char... 2016-03-07, 2011👍, 0💬

How can I specify a variable width in a scanf format string?
How can I specify a variable width in a scanf format string? You can't; an asterisk in a scanf format string means to suppress assignment. You may be able to use ANSI stringizing and string concatenation to construct a constant format specifier based on a preprocessor macro containing the desired wi... 2015-10-26, 2005👍, 0💬

Does the sizeof operator work in preprocessor if directives?
Does the sizeof operator work in preprocessor if directives? No. Preprocessing happens during an earlier phase of compilation, before type names have been parsed. Instead of sizeof, consider using the predefined constants in ANSI's &lt;limits.h>, if applicable, or perhaps a ``configure'' script.... 2016-02-03, 2004👍, 0💬

What does the message warning macro replacement within a string literal mean?
What does the message warning macro replacement within a string literal mean? Some pre-ANSI compilers/preprocessors interpreted macro definitions like #define TRACE(var, fmt) printf("TRACE: var = fmt\n", var) such that invocations like TRACE(i, %d); were expanded as printf("TRACE: i = %d\n", i); In ... 2015-12-14, 2004👍, 0💬

When I call malloc to allocate memory for a pointer which is local to a function ....
When I call malloc to allocate memory for a pointer which is local to a function, do I have to explicitly free it? Yes. Remember that a pointer is different from what it points to. Local variablesare deallocated when the function returns, but in the case of a pointer variable, this means that the po... 2016-03-31, 1997👍, 0💬

I am trying to use the ANSI stringizing preprocessing operator ...
I'm trying to use the ANSI ``stringizing'' preprocessing operator `#' to insert the value of a symbolic constant into a message, but it keeps stringizing the macro's name rather than its value. It turns out that the definition of # says that it's supposed to stringize a macro argument immediately, w... 2015-12-16, 1988👍, 0💬

I have a program which mallocs and later frees a lot of memory ...
I have a program which mallocs and later frees a lot of memory, but I can see from the operating system that memory usage doesn't actually go back down. Most implementations of malloc/free do not return freed memory to the operating system, but merely make it available for future malloc calls within... 2016-03-28, 1982👍, 0💬

How can I use a macro argument inside a string literal in the macro expansion?
How can I use a macro argument inside a string literal in the macro expansion? Some pre-ANSI compilers/preprocessors interpreted macro definitions like #define TRACE(var, fmt) printf("TRACE: var = fmt\n", var) such that invocations like TRACE(i, %d); were expanded as printf("TRACE: i = %d\n", i); In... 2016-01-22, 1973👍, 0💬

<< < 1 2 3 4 5 6 7 8 9 10 … > >>   Sort: Date

.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