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

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212 views

C Linked List Implementation Pointer vs. Pointer-to-Pointer Consistency

To get some practice in C, I'm writing some basic functions for operating on a linked list of ints. I started out with functions that accepted as a "list" a pointer to the head node. Now, I find ...
2
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2answers
85 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. ...
8
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5answers
1k views

When does it make sense to compile my own language to C code first?

When designing an own programming language, when does it make sense to write a converter that takes the source code and converts it to C or C++ code so that I can use an existing compiler like gcc to ...
3
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3answers
419 views

Separating Code into Smaller Files in C

I am in the process of cleaning up my code and making it easier to maintain. I am doing this by turning my 5000+ line file into separate smaller files. I have successfully created separate source and ...
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1answer
356 views

Illustrate Meaning of : gcc -g programName.c

To debug a C program using gdb effectively it is required to compile it first using the command: gcc -g programName.c otherwise on using simply gcc programName.c and running we are unable to ...
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1answer
210 views

What are the current (2014) naming conventions in C for file names? [closed]

This is about C, not C++. Googling this brings this result up immediately: https://www.doc.ic.ac.uk/lab/cplus/cstyle.html#N10081. In that article, the authors are saying very clearly that all source ...
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2answers
360 views

Given a number X, how do I find from an array of numbers, a unique combination that adds up to X and has the lowest sum of squares?

Given the number 15 and the array [1, 2, 3, 4, 5, 6] Possible combinations (sum=15) would be: [1, 2, 3, 4, 5] [2, 3, 4, 6] [1, 3, 5, 6] [4, 5, 6] Their respective sum of squares would be: 55, 65, 71 ...
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2answers
447 views

Infinite while loop CPU usage

I'm coding an script in C, which is going to check constantly an array of events, the idea is to check if the Date and time of certain event is equal to de current time and trigger something, i'm ...
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5answers
123 views

Does it make sense to have a separate init function?

I'm created an opaque type and I have two options for its management. The first looks like this: type_t *a = type_init(); int err; err = type_do(a, "foo", "bar", FLAGBIT1|FLAGBIT2, NULL); if (!err) ...
1
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1answer
910 views

The advantage of using __attribute__((aligned( )))

I found in more than one SIMD program the instruction __attribute__((aligned(16))) . When I looked for an explanation I found The keyword attribute allows you to specify special attributes of ...
7
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5answers
650 views

Undefined behavior, in principle

Whether in C or C++, I think that this illegal program, whose behavior according to the C or C++ standard is undefined, is interesting: #include <stdio.h> int foo() { int a; const int ...
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3answers
211 views

How to abide the “allocate in caller” rule when the size is computed in the callee?

Let's say we have an opaque type handle_t that is managed through a simple interface with functions such as: handle_t *handle_init(void); int handle_do(handle_t *); void handle_free(handle_t *); ...
4
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2answers
119 views

Defining error codes

We are designing an error-handling framework for a cryptographic library written in C. The approach we are taking is that relatively few errors are propagated back to the user since on most occasions ...
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1answer
195 views

Ambiguous If-else nested block in C without braces [closed]

Consider the following code in C: if(34) if(0) printf("Stat1"); else printf("Stat2"); Here,the first if condition is true,while the second if condition is ...
1
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1answer
437 views

Polymorphic engines in C and/or C++ [closed]

I stumbled across polymorphic engines and I don't know anything about them. However, I am curious about how they are written. Every example that I've looked up writes them in assembly, my assembly is ...
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1answer
98 views

Buffer-overflow vulnerabilities that a static code analyser won't pick up [closed]

I'll use FlawFinder in this example. FlawFinder is a static code "analyser" tool that examines C/C++ source files and outputs warnings/hits if a vulnerability was identified. The way it does this is ...
3
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2answers
317 views

On concatenating adjacent string literals

C and C++ compiles adjacent string literals as a single string literal. For example this: "Some text..." "and more text" is equivalent to: "Some text...and more text" In other languages like C# ...
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1answer
118 views

Uniqueness of for loop [closed]

How does the for loop function is implemented so that it can accept ; as parameter separator rather than , which is trivial in normal functions.
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5answers
705 views

Are C static libraries frowned upon? [closed]

There are 2 arguments for having shared libraries: It helps reduce disk space. When a shared library is updated, all the binaries depending on it get the update. There is mainly one drawback for ...
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2answers
219 views

Microchip XC8: How to pack code against an upper limit?

I have a project for a PIC16F1454 that needs some custom linking. Basically, I've separated my code into two parts that can be downloaded separately in the field and thus update (almost) all of the ...
4
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1answer
570 views

Why did GCC switch from Bison to a recursive descent parser for C++ and C?

Was there a language change that required it or some practical reason why Bison was no longer appropriate or optimal? I saw on wikipedia that they switched, referring to the GCC 3.4 and GCC 4.1 ...
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2answers
197 views

In which stage of compilation is “typedef” resolved by the compiler?

There are different stages of compilation Such as Preprocessing stage Syntax analysis Semantic analysis Intermediate Code generation Machine Code generation Optimization Linking My question here ...
3
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1answer
143 views

How to fix legacy code that uses <string.h> unsafely?

We've got a bunch of legacy code, written in straight C (some of which is K&R!), which for many, many years has been compiled using Visual C 6.0 (circa 1998) on an XP machine. We realize this is ...
4
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7answers
3k views

Why do we need to include the .h while everything works when including only the .cpp file?

Why do we need to include both the .h and .cpp files , while we can make it works with making just a .cpp file and then including it . For example, Creating a file.h containing declarations, then ...
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12answers
6k 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 ...
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1answer
69 views

Macro guard in Objective-C

I have noticed that many famous libraries written in Objective-C (eg. AFNetworking) use the macro guard inside their header files. Im aware that the #import directive, which works exactly like ...
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1answer
265 views

What are steps in making an operating system in C ? [duplicate]

I am trying to make an my own OS. This is for educational purpose only, so that I get to understand the internals as well as get a good idea of low level programming. I have some prior application ...
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2answers
219 views

Is goto to improve DRY-ness OK? [duplicate]

My code has many checks to detect errors in various cases (many conditions would result in the same error), inside a function returning an error struct. Instead of looking like this: err_struct ...
0
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1answer
111 views

comparison of an unsigned variable to 0

When I execute the following loop : unsigned m; for( m = 10; m >= 0; --m ){ printf("%d\n",m); } the loop doesn't stop at m==0, it keeps executing interminably, so I thought that ...
3
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3answers
162 views

Why are packed structures not part of the C language?

Every C compiler offers the option to "pack" C structures (e.g. __attribute__ ((__packed__)), or #pragma pack()). Now, we all know that packing is required, if we'd like to send or store data in a ...
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votes
1answer
318 views

Calculate Pi to N number of places [closed]

I am trying to work out how to calculate Pi to N decimal places, I think the default DP's for a float/double is 5 and then you have setprecision() however these are obviously inadequate, I need ...
2
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1answer
185 views

How to store satellite data in C data structutres

I've been reading through Introduction To Algorithms 3rd Ed, and am really enjoying the material; however, I am having difficulty in implementing some practical situations. It's not the theory, or ...
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3answers
628 views

Reconstructing a huffman tree using minimal information in the header

I'm writing a huffman encoding program in C. I'm trying to include the least amount of information in the header as possible, I know the simplest way to decompress the file in the header would be to ...
3
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3answers
555 views

C/C++: Which conversion warnings make sense in practice?

C/C++ implicit conversions can cause bugs. Here's one example: int foo, bar; scanf("%d", &foo); scanf("%d", &bar); float foobar = foo / bar; If I input 7 and 2, it's not 3.5 as expected - ...
6
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2answers
484 views

C programming practice, passing a pointer to a function [closed]

Consider the following C function which takes as argument a string, which is then stored inside a struct: struct mystruct* usestring(char* string) { struct mystruct *struct; struct = ...
1
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2answers
302 views

Implementing a simple controller in embedded C

Is there a known method or pattern to implement a simple controller for an MVC design in pure C or the switch case approach is the standard? Background : I have an embedded application and I'm ...
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2answers
216 views

boolean operations in C using bitfields

I am trying to implement boolean data type in C. Basically, I am working with sets. The following code can be used to access each bit but I am unsure whether I can represent sets using this method. ...
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1answer
170 views

What is this boolean law?

A friend of mine has shown sometime ago the name of the below boolean technique/law but I forget that name unfortunately. Does someone know what it's called? example in C language: !(a || b) It's ...
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2answers
252 views

Reading assembly useful for insights when writing C/C++? [closed]

While in most cases its not necessarily, recently I have taken to reading the generated assembly of my C code every so often, when I'm curious as to the kinds of optimizations my compiler is making. ...
5
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2answers
267 views

Processor architectures for testing C/C++ portability

Currently I'm working on a C/C++ code-base which is fairly portable, it can compile on most Unix like systems as well as MS-Windows (MSVC), using various popular compilers. Previously I've found ...
11
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2answers
4k views

Why does C use the asterisk for pointers?

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 ...
20
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3answers
4k views

Why Increment Pointers?

I just recently started learning C++, and as most people (according to what I have been reading) I'm struggling with pointers. Not in the traditional sense, I understand what they are, and why they ...
1
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2answers
118 views

Is there a stricter strtoull() in any ubiquitous C library?

I want a function that will interpret a string as a strictly unsigned integer, failing when the string overflows, represents a negative number, or does not represent a number. strtoull() does set ...
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1answer
117 views

Implementing keyword “const” [closed]

A constant pointer is a pointer which points to a fixed memory location throughout.The question is how do you ensure that this behavior is ensured without using the keyword constant while declaring ...
1
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4answers
188 views

What should I do and know before I start writing C? [closed]

I have a college degree in CS, and learned about Java and OCaml. Java was used as introduction, and in most CS classed, except the theoretical ones. OCaml was part of learning a different programming ...
3
votes
2answers
200 views

Why do binary files load quicker than alphanumeric text files?

I've noticed that when I load/store large data files in a binary format, the program runs much faster than if I load data from an ASCII encoded file. Why is this the case? The data in my case is ...
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1answer
206 views

Which is the more testable C function implementation?

I write code in C. I have been striving to write more testable code but I am a little confused on deciding between writing pure functions that are really good for testing but require smaller functions ...
7
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4answers
310 views

Omitting “destructors” in C is taking YAGNI too far?

I'm working on a medium embedded application in C using OO-like techniques. My "classes" are .h/.c modules using data structs and function pointers structs to emulate encapsulation, polymorphism, and ...
26
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10answers
4k views

When I test out the difference in time between shifting and multiplying in C, there is no difference. Why?

I have been taught that shifting in binary is much more efficient than multiplying by 2^k. So I wanted to experiment, and I used the following code to test this out: #include <time.h> #include ...
1
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3answers
103 views

Handling leaves in tree-based menus

Tl;Dr Given a language with no polymorphism how to you elegantly modify the behavior of a leaf in a tree data structure. Context I'm programming an application in C for a microcontroller and I'm ...