C is a general-purpose computer programming language used for operating systems, games and other high performance work.

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Complex iterators in C

note: this was originally asked on SO. Part of my current project involves iterating over sequences that don't necessarily exist. For example, I have something similar to a relational database in ...
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3answers
300 views

Understanding the concept of “arguments” and “parameters”

In the third last paragraph at page number 26 of the ebook "The C Programming Language" the author(s) say, "We will generally use parameter for a variable named in the parenthesized list in a ...
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1answer
213 views

Endianness at bit level

I am learning the union and struct and I wrote the code below. What I do not understand is why the output is different when I change from a little endian to a big endian machine. My understanding is ...
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3answers
516 views

How to extract the active code path from a complex algorithm

I have been puzzled lately by an intruiging idea. I wonder if there is a (known) method to extract the executed source code from a large complex algorithm. I will try to elaborate this question: ...
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1answer
88 views

What's an effective threading structure for NIO and server performance in C/C++? [closed]

I run into this issue where if I do a read to check for data too often, my CPU skyrockets, and if I don't check often enough, it's slow for client performance. What's an effective way to deal with ...
6
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4answers
380 views

When did Undefined Behavior in C jump the causality barrier

Some hyper-modern C compilers will infer that if a program will invoke Undefined Behavior when given certain inputs, such inputs will never be received. Consequently, any code which would be ...
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5answers
5k views

Should I initialize C structs via parameter, or by return value? [closed]

The company I work at is initializing all of their data structures through an initialize function like so: //the structure typedef struct{ int a,b,c; } Foo; //the initialize function ...
2
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3answers
166 views

API to get data, caller may not know how much? How to allocate buffer size

I am writing a C API for retrieving data from a hardware device. The data will be returned as a string with approximately 30 bytes of text per item. The problem is there may any number of items. ...
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2answers
505 views

Why dynamic memory allocation functions in C returns void*?

Consider the prototypes of C's dynamic allocation functions malloc - void* malloc(size_t size); calloc - void* calloc(size_t n,size); realloc - void* realloc(void* ptr,size_t newsize); Now a ...
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6answers
873 views

Replacing C with JavaScript as an introductory programming language [closed]

I am a new teacher at polytechnic where we teach web development and basic software programming. For years, the institution where I teach have taught C as their introductory programming language to ...
3
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0answers
380 views

Fast fixed-size (256 bit) integer modulo/division

What is the fastest way to divide two 256-bit integers? They are represented as an array of 26-bit words, each stored in 32-bit integers. I have access to a 64-bit type if that's useful. It seems ...
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0answers
69 views

A callback for when data is received?

So, my understanding is that the Kernel could receive TCP at any time, and that generally a C program asks the Kernel synchronously/asynchronously if it has data available. Would it be possible for a ...
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1answer
226 views

What would be a reason not to embed JS in C? [closed]

I'm working on an opensource application that processes JSON in C, because I would like to make it easier for people to help me in the project and because JSON is so close to JS. I want to embed a JS ...
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2answers
86 views

What should JITed bytecode do exactly?

I'm working on a VM (and a scripting language for it) that I plan to implement JITing for. I'm only working on the "plumbing" of it now, but I don't want the JIT compiler to be an afterthought. ...
3
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1answer
296 views

What is the motivation for casting a pointer into a integer?

I'm doing some changes in the Linux kernel code and have noticed a pointer being cast into integer. Check out buf below (full code): snd_pcm_sframes_t snd_pcm_lib_read(struct snd_pcm_substream ...
22
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12answers
7k views

Why does void in C mean not void?

In strongly-typed languages like Java and C#, void (or Void) as a return type for a method seem to mean: This method doesn't return anything. Nothing. No return. You will not receive anything from ...
2
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2answers
475 views

How small is the footprint of a small C compiler?

This week I could optimize using a reduced C library that allowed a drastic shrinkage in code size - from about 60 K to about 6 K and then we could load the code in the 8 K on-chip memory of an FPGA ...
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2answers
221 views

In C, how are functions accessible if they're not inline or called by #include? [closed]

I'm looking at code that somehow calls a library but I don't see it calling any of the library's headers at any point. I've done searches within the code and I don't see anywhere the functions, ...
13
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1answer
440 views

Why using sizeof of type to calculate the number of elements in an array is considered inferior to using sizeof of an element?

I'm reading "King K.N's C programming" and I'm reading the following statement: We discussed using the expression sizeof(a)/sizeof(a[0]) to calculate the number of elements in an array. The ...
3
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3answers
369 views

A list of the most important areas to examine when moving a project from x86 to x64? [closed]

I know to check for/use asserts and carefully examine any assembly components, but I didn't know if anyone out there has a fairly comprehensive or industry standard check-list of specific things at ...
73
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15answers
31k views

What makes C so popular in the age of OOP? [closed]

I code a lot in both C and C++, but did not expect C to be the second most popular language, slightly behind Java. TIOBE Programming Community Index I'm curious as to why, in this age of OOP, C is ...
2
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2answers
557 views

Is there a better way to organize my module tests that avoids an explosion of new source files?

I've got a neat (so I thought) way of having each of my modules produce a unit-test executable if compiled with the -DTESTMODULE flag. This flag guards a main() function that can access all static ...
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2answers
249 views

How does the post increment operator work in GNU C? [closed]

While the run the below program in Turbo C compiler, I am getting the expected output, however, when I run the same program it using "gcc" compiler in linux, it is giving an unexpected output! int ...
5
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1answer
479 views

How to store satellite data in C data structures

I've been reading through Introduction To Algorithms 3rd Ed, and I am having difficulty in implementing some practical situations. It's not the theory, or implementing the internals of the data ...
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3answers
131 views

How much can you detect undefined behaviour using testing [closed]

I hope this question fits this site. You may know you can't detect undefined behaviour in C using compilers - and some tools (static analysis) can help you detect it. My question is more empirical - I ...
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1answer
137 views

floating-point number stored in float variable has other value [duplicate]

I'm reading a book about C programming By "King.K.N" and I'm reading the following statement: If we store 0.1 in a float variable, we may later find that the variable has a value such as ...
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6answers
1k views

I believe I have mixed C and C++ code when I shouldn't have; Is this a problem and how to rectify?

Background/Scenario I started writing a CLI application purely in C (my first proper C or C++ program that wasn't "Hello World" or a variation thereof). Around midway through I was working with ...
3
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1answer
937 views

How do C/C++ programs get ported to different platforms? [closed]

Java applications can run on different platforms because they always run on top of a Virtual Machine specifically developed for each platform. So, there's no native installation, you just drop the ...
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2answers
281 views

What's the simplest way to deal with events in C in this situation?

I'm writing a text-based game, in C. I want the game to handle NPCs movement and actions in the background, while the user is making his moves. I'd also use time-based events to tell the user when ...
16
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2answers
488 views

Has variable width types been replaced by fixed types in modern C?

I came across an interesting point today in a review over on Code Review. @Veedrac recommened in this answer that variable size types (e.g. int and long) be replaced with fixed size types like ...
9
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5answers
2k views

Simple and clean way of comparing three numbers

I've got some code that has a sequence of ifs that work, but just feel messy. Basically, I want to choose the largest of three integers and set a status flag to say which was chosen. My current code ...
5
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4answers
2k views

What do other languages offer when it comes to infrastructure technology that could indicate its advantage over C in the future?

I have been going through interview questions and I saw one which made me stop and think for a while. It starts with a quote and asks about your interpretation and whether you agree or not. "For ...
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8answers
2k views

What stops C from being compiled/interpreted/JIT'ed?

Java is often praised for its amazing portability, which I presume is because of the JVM. My question is what stops C from being being compiled/interpreted/JIT'ed.., if so, C can also be write once ...
7
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1answer
1k views

“Read” a file without using a file pointer

I was asked this question in an interview. I'm somehow supposed to "read" a file into my C program as input without using a file pointer (including "f" functions, e.g. fgets, fscanf etc.). I'm also ...
1
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1answer
96 views

Best practices for tracking multiple pieces of data in a program

I have a project in C (don't ask why but it needs to be in C), where I need to track multiple pieces of data and commands for different modules. Some actions that the program will take depend on the ...
8
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2answers
3k views

What is the difference between function() and function(void)?

I have heard that it is a good practice to write functions that do not receive anything as a parameter like this: int func(void); But I hear that the right way to express that is like this: int ...
2
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1answer
92 views

Are there any problems with defining a single-source “module” in C using conditional compilation to separate the “header” from “source”

I'm writing a project that I want to keep small in the sense of being very densely-coded and a single source file. But it's growing large enough that navigating the file is becoming tiresome, so I ...
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2answers
133 views

Multiple threads making call to precompiled library

I have been asked this question in an interview and I thought to take advice from you guys. Say I have a pre-compiled library which references to some function say "strtok". There is no source code ...
2
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2answers
208 views

What is the point of designing Lua C APIs?

I am a newbie of Lua. After studying some Lua C APIs examples, I am a little confused. I can see the Lua C API is used for processing Lua scripts: ...... lua_State *L = luaL_newstate(); ...
5
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1answer
423 views

Kth selection routine - Floyd Algorithm 489

I have recently come across a promising Kth selection routine that reportedly outperforms quickselect the Floyd, Rivest Select routine. This Wikipedia article provides a pseudocode version which I ...
1
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0answers
358 views

Why C doesn't have better notation for pointers? [duplicate]

The * symbol is used for three different purposes multiplication Pointer declaration Pointer dereferencing. Why designers of C kept this notation? In other words, wouldn't it be nice if there ...
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2answers
102 views

If I #include a file, do I need to have a valid path to any headers #included in the included file [closed]

For example, if I have created a library, libcommon, which uses some other custom, but widely used library in a specific field (some_other), like this: libcommon.h #ifndef LIBCOMMON_H #define ...
27
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10answers
8k views

What is the “type” of data that pointers hold in the C language?

I know that pointers hold addresses. I know that pointers' types are "generally" known based on the "type" of data they point to. But, pointers are still variables and the addresses they hold must ...
16
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2answers
5k views

Why does C use the asterisk for pointers? [closed]

I'm just now learning about C. I find it odd that the creators chose the asterisk (*) as the symbol for pointers rather than a symbol that actually looks like a pointer (->). Considering how ...
1
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1answer
533 views

Help me construct a list of best approaches for new C and C++ developers [closed]

Not specific code writing practices. Please also include reasoning. My start: use GCC or Clang gcc because it is unchallenged in the amount of static checking it can do (both against standards ...
2
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1answer
242 views

C Module - Where to put prototypes and definitions that do not belong to the public interface?

Since I am mainly an Electrical Engineer, forgive me if I am somewhat off with some terminology. I am currently programming a display driver/interface module. And like so many times before, I have ...
38
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6answers
5k views

How to think as a C programmer after biased with OOP language? [closed]

Previously, I've only used Object Oriented Programming languages (C++, Ruby, Python, PHP), and am now learning C. I'm finding it difficult to figure out the proper way to do things in a language with ...
7
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4answers
2k views

The need for Explicit Type Conversion in C#

Consider the following code: DerivedClass drbObj = (DerivedClass)obj; Here obj is of type Object and this is reasonable since Object is the base type of every Class in C#. Here, since the type of ...
6
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4answers
5k views

What is important when optimising for the CPU cache (in C)?

Reading these two questions, I see that understanding CPU caching behaviour can be important when dealing with large amounts of data in memory. I would like to understand the way the caching works to ...
5
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2answers
148 views

What is a reasonable level of detail for a style guide? [closed]

We are developing embedded software for an automotive product in ANSI-C in a large team. Yesterday, in our regular code review, we had a general discussion about the style of our code. We have a ...