Questions tagged [c]
C is a general-purpose computer programming language used for operating systems, games and other high performance work.
-1
votes
1answer
45 views
Makefile: Dev and Release
In Git, I have a master branch (release) and a dev branch (development) for a C project.
In the master branch, I want gcc to only be passed the compiler flag -Os (optimize for speed) and not -ftest-...
0
votes
1answer
50 views
How to safely walk a list to remove an element as well as associated elements safely
I have a single linked list of elements. Each element has a unique ID (positive integer) and a type. Each element may have a "sister" element, associated by its ID, that may also be in the list. The ...
2
votes
0answers
60 views
Dynamically load user code from a common library
My project aims to provide a common interface between multiple different HDL simulators, so users can write test benches that will work no matter the simulator used. In this situation, it is the ...
0
votes
2answers
69 views
Understanding Context Free Grammar using a simple C code
I'm trying to understand the difference between terminal and non-terminal values in a real language. I wasn't able to find enough examples on real language CFGs on the internet, most examples are ...
0
votes
1answer
42 views
Subdomain matching
I am working on a small plugin for a DNS server. I have a static list of domain (sometimes subdomains too) names:
gaming.xyz.com
facebook.com
mail.example.com
blog.example.com
I want to check if a ...
0
votes
1answer
105 views
Folder structure for a C project [closed]
I am wondering what is the recommended folder structure for a C project. I read several posts about using src, include, test, build folders. But what if I want to structure the project in modules?
...
3
votes
2answers
123 views
Best way to model UTC time and deltas in embedded C
I'm getting ready to do some work on an embedded firmware prototype that has a GPS chip attached to it (straight C on an arm0, no OS).
I'm torn on how to model UTC instants and time deltas. ...
-5
votes
1answer
102 views
Why does the C compiler use memory for simple arithmetic operations
Assume the following C code:
#include <stdio.h>
int main()
{
int a = 5;
int b = 15;
return a + b;
}
Compiling it using gcc creates an assembly code which includes the following:
...
12
votes
3answers
497 views
Is using C/C++ macros as a shortcut for conditional compilation a good practice?
Let's say I want to have several types of output messages in my code. One of them is DEBUG, which is printed only, when the code is compiled in Debug mode.
Usually I'd have to write something like
#...
-2
votes
1answer
87 views
How can I find the address of my first memory location
If i'm writing my own kernel I will have access the the physical memory (instead of a virtual memory).
Now assume I want to make a loop starting from the first memory location until the last one and ...
-3
votes
0answers
64 views
How does an Operating System gets allocated its first memory space [duplicate]
Going through osDev.org, I managed to write a small kernel that outputs a memory address, similar to this:
#include <stdio.h>
int main()
{
size_t a = 2;
size_t *p = &a;
printf("...
-3
votes
2answers
173 views
How are memory addresses created?
#include <stdio.h>
int main()
{
size_t a = 2;
size_t *p = &a;
printf("%p\n", p);
}
The above code will print the memory address of a. I understand that within an OS, this ...
2
votes
5answers
400 views
Why is there a limit on data types
I know that an int for example has a max value of 2,147,483,647 and is stored in 4 memory slots (each 8 bits and a total of 32 bits or simply a word).
Int can be loaded into a 32 bit Register just ...
2
votes
4answers
163 views
Is an Array Index content stored in one memory address?
Assume in C we have the following array of one item:
int a[] = {2000};
2000 in binary would be:
11111010000
If each memory address can hold 1 byte (8 bits) of data, then howcome
in some tutorials, ...
15
votes
2answers
3k views
Is converting a C++ method to a C function with a pointer argument an acceptable pattern?
I use C++ on ESP-32. When registering a timer I have to do this:
timer_args.callback = reinterpret_cast<esp_timer_cb_t>(&SoundMixer::soundCallback);
timer_args.arg = this;
Here the timer ...
2
votes
1answer
162 views
Handling hardware dependency while unit testing
I am writing a driver for an IMU sensor using test driven development approach. Communication protocol of choice is SPI. Using CubeMX and STM32F415 processor, SPI interface is implemented in ...
-1
votes
1answer
187 views
Few unusual C/C++ declarations
I came across this Enum and Struct declarations in a project supposedly done by an expert.
The declarations / definitions are little different than what im used to so far.
enum EnumKeys {
KEY_MENU ,...
1
vote
1answer
118 views
Find a string in list of strings
Background:
I am writing an application for a small embedded device. There is a static list of strings: currently about 500 strings and string length is 12 characters on average. The list might ...
2
votes
1answer
114 views
How to abstract HAL in embedded test driven development?
Recently I've been reading into topic of test driven development and decided to give it a go with a sensor driver I need. Sensor uses SPI interface and I will implement this driver on STM32F415 ...
5
votes
3answers
174 views
How to handle repetitive mallocs/frees in a DRY way in C
So I have a function which is like a constructor for my structure:
MyStructure* CreateMyStructure(...)
{
MyStructure *my_structure;
double *data;
int *colind, *rowptrs;
data = malloc(...
3
votes
1answer
205 views
Why do we need to specify the type of data a pointer will hold, if all pointers are the same [duplicate]
Why do we need to specify the type of the data whose address, a pointer will hold, if all pointers are the same.
Since all pointers store addresses.
Also, the amount of space a pointer will require in ...
1
vote
2answers
152 views
Using C coding conventions in C++ code [duplicate]
I'm working on a large codebase whose core modules are in C and extension modules are in C++. We have a coding convention for C code but I'm being told that we need to enforce the same coding ...
148
votes
7answers
23k views
Was the C programming language considered a low level language when it came out?
Currently C is considered a low level language, but back in the 70's was it considered low level? Was the term even in use then?
Many popular higher level languages didn't exist until the mid 80's ...
2
votes
0answers
188 views
Embedded software architecture - What is the difference between DAL and HAL?
I'd like to know what the difference is between hardware abstraction layer (HAL) and data abstraction layer (DAL) when speaking about embedded software. I might have the abbreviations wrong though...
...
6
votes
1answer
245 views
Is it a good practice to redefine unavailable keywords as macros?
Is it a good practice to redefine unavailable keywords with macros?
I use GCC 4.8 in one of my projects which isn't exactly C11 standard compatible. At least not the extent of 4.9. But there are some ...
2
votes
3answers
394 views
High level overview of how printf() works with Windows OS
I asked this question on an IRC channel, sadly I am going around in circles.
I am aiming for a high level overview (but with some technical details if necessary) on how a function such as printf() ...
0
votes
0answers
90 views
Cycle accuracy through the use of a microtable for an 8 bit CPU emulation?
I'm in the process of writing a 8 bit cpu emulator and currently have a jump table for different opcodes. I want to move this over to be cycle accurate and was wondering what the best approach would ...
1
vote
1answer
97 views
Embedded Systems: Designing an API that monitors an address
This question was tossed as a starting point in a technical interview at a semi-conductor company. I guess there are no right ans - the purpose of this open ended question is to gauge the engineer's ...
0
votes
0answers
105 views
Conflicting opaque struct implementations as part of a C API
I am currently toying with the idea of designing a somewhat sophisticated C API. I have looked around existing APIs and found an interesting approach revolving around opaque structs. Specifically, I ...
3
votes
1answer
402 views
What tasks does a memory barrier enforces other than preventing the re-ordering of instructions?
I know that a memory barrier prevents the re-ordering of instruction from before to after and from after to before the memory barrier, for example if I have the following instructions:
instruction 1
...
-4
votes
1answer
245 views
TIOBE Index: why c++ is in 3rd place and C is having more land in the last year?
Searching for c++ ranking on the TIOBE index, I was stumped to see that C is in front of C++, and from 2017, C took a leap. Could someone explain why?
2
votes
1answer
132 views
How did graphics programming evolve over time? [closed]
There isn't a single blog/site out there that shows how graphics technologies evolved over time, how and why they became what they're now. If anyone can shed some light on it, it would be great.
See, ...
1
vote
1answer
332 views
Difference between header files and interfaces
I wanted to know whether the header files in c and c++ have same function as that of interfaces used in Java? If not what is the difference between header file and interface?
-1
votes
1answer
146 views
Pointers and Values in C
I do a lot of work in various languages, most of which are scripting languages such as JavaScript, Shell Scripting, PHP and so on. But I do also work a lot with Java, which is closer to a more "real" ...
0
votes
2answers
199 views
copying of memory vs pointer to memory in real time systems
While working in a multi-threaded environment, then data sharing seems to be a good option to pass data between threads.
While working with real time systems it is apparently advisable to go with ...
1
vote
1answer
247 views
Declaring functions using macros?
Is it generally encouraged or discouraged to create a pre-processor macro in C, that facilitates the creation of many functions with the same signature (differing only in name). For instance, instead ...
0
votes
4answers
332 views
Why does C provide both the comma operator and the semicolon to separate statements?
Both the comma operator and the semicolon can be used to separate statements. Let's consider this simple code:
#include <stdio.h>
void do_something(int*i) {(*i)++;}
int main() {
int i;
...
2
votes
2answers
213 views
API for data structure with indices, size_t vs int?
For a data structure with indices (e.g. an array list, a dynamic array, etc...), should the indices be of type size_t or int? Is there a clear reason to use one over the other?
fooGetByIndex(struct ...
0
votes
0answers
36 views
First DSP project: Amplify digital audio input on Windows 7 on real-time
I want to learn bit about digital signal processing (DSP) with software. As the introduction to the field, I want to make simple real-time PC microphone amplifier, which amplifies the digital ...
4
votes
4answers
1k views
What is the correct way of adding third-party code into a C or C++ project?
I want to incorporate some open source libraries into my C project. This is the first time I do that, so I don't know what is the right or most common way of doing it.
I see two possible paths I can ...
4
votes
4answers
576 views
Rely on compiler to remove unused code or #ifdef out?
I am working on a USB stack in C. This stack will be open source and used in various different projects.
Various configuration options are available, which enable or disable large chunks of code and ...
1
vote
0answers
107 views
How could an fresher start doing changes in thousand lines code immediately after joining? [duplicate]
Well I am newly graduated and placed in a small scale project based company. When I joined , the boss (project head) gave me project code for understanding what work I will be doing hence forth. I ...
1
vote
1answer
151 views
Handling error in multiple state machines in embedded systems in C
I have few state machines which run "concurrently" in a super loop.
do
{
state_one();
state_two();
state_three();
/* The point I want to deal with the error */
} while(1);
Each of these ...
-3
votes
2answers
214 views
Why we use top== -1 for implementation of stack using simple array?
I am a newbie at data structures.
I have read an implementation of a stack using a simple array. The algorithm for this implementation is presented below.
Stack implementation in terms of an array
...
-1
votes
2answers
382 views
Should I use parenthesis around every operators?
The facts
This is a very similar question to this one, but here I am talking about a more general case the MISRA-C3 Rule 5.0.2 or the SEI CERT C EXP00-C rule (more permissive).
Within MISRA-C3 I ...
4
votes
1answer
392 views
Is CSS inspired from C? [closed]
Maybe I'm not the first to ask this, but I've searched up and down the stack and I am yet to get an answer to my question. I have learnt CSS, and I also have a basic idea of the C programming language....
1
vote
0answers
164 views
How does the BIOS detect the size of installed memory? [closed]
I'm writing a little toy operating system using a mix of C and Assembly (It's not meant to be good/fast, just meant to learn from). I know that I can issue an interrupt (I think it's INT 0x15) to ...
14
votes
4answers
1k views
How do you code something when you have no idea how it actually works? [closed]
I have recently learned C and want to start a project to solidify my knowledge. I've settled on making a very simple text editor, something like vim. The problem I face is that I genuinely have no ...
-2
votes
1answer
162 views
Is pointer holds a base address or it holds whole limits? [closed]
We have
int i;
which have 4 bytes lets have address from 1000 to 1004.
if we declared a pointer
int* p;
p = &i;
now is the pointer holds only 1000 or from 1000 to 1004?
The pointer holds ...
2
votes
3answers
201 views
Are Instanced APIs a Problem in a C Interface?
So an Instanced API is one that behaves like an object. So for example:
foo* GetInstancedAPI();
void MemFuncSetter(foo* fooThis, const int arg);
int MemFuncGetter(const foo* fooThis) const;
This is ...
