Say my code looks like this: gpios.h: #define GPIO_BASE 0x08000100 #define GPIOA ((GpioRegs *) (GPIO_BASE + 0x04)) #define GPIOB ((GpioRegs *) (GPIO_BASE + 0x0C)) #define GPIOC ((GpioRegs *) (GPIO_BASE + 0x14)) switches.h: #define SWITCH1_PORT GPIOA // On this particular system, both switches #define SWITCH2_PORT GPIOA // are on the same port. This could change in the future switches.c: #if SWITCH1_PORT == SWITCH2_PORT // Code is a lot simpler if both switches are on the same port #else // Otherwise do it the hard way #endif SWITCH1_PORT and SWITCH2_PORT are both constants at comp ..read more

PyObject *python_module; char *module_filename = "/mnt/USB3/C/Python_from_C/python_processes"; Py_Initialize(); python_module = PyImport_ImportModule(module_filename); if(python_module == NULL) { printf ( "Failed to load module \"%s\"\n", module_filename ); getchar(); } ` The python_processes.py file exists. The returned module is always NULL. The PyImport_ImportModule() function emits no error message, I have tried many Python initialization schemes (there are rather too many) and all result in the module not being loaded. Here is another attempt. This ..read more

sigprocmask(2) says: Each of the threads in a process has its own signal mask. , but also: The use of sigprocmask() is unspecified in a multithreaded process; see pthread_sigmask(3). pthread_sigmask(3) states, that: The pthread_sigmask() function is just like sigprocmask(2), with the difference that its use in multithreaded programs is explicitly specified by POSIX.1. Other differences are noted in this page. , but than there are no notes about that. However https://docs.oracle.com/cd/E19120-01/open.solaris/816-5137/gen-19/index.html says, that: The call to sigprocmask() in a multithrea ..read more

For personal use, I'm coding an additional layer on SDL2, which includes an event manager. It correctly detects every type of event, except SDL_WINDOWEVENT_CLOSE. After trying to debug my code, I realized that SDL2 actually never fires that event on my device... So there's no problem when I have only 1 window (because SDL_QUIT is thrown instead), but when I have several windows I just can't detect when a window closing is requested, and I have to ctrl+C my program from the shell to have SDL_QUIT fired manually. Here is a minimal working example : #include <stdio.h> #include <SDL2/SDL ..read more

In an attempt to help learn C I've been trying to write a simple calculator, but I'm stuck on the issue of scanf not assigning the inputted value to a variable. I've seen people recommend fgets over scanf but that brought more issues so I decided to stick with scanf for now. the reason I have all the getchar(); and " %d\n" included in there is because the program would skip directly past those inputs otherwise. Thank you. #include <stdio.h> #include <string.h> int main() { int numberOne; int numberTwo; int result; char operation[8]; printf("Enter your first nu ..read more

I'm trying to solve this question: Given an array of integers nums and an integer target, return indices of the two numbers such that they add up to target. You may assume that each input would have exactly one solution, and you may not use the same element twice. You can return the answer in any order. Example 1: Input: nums = [2,7,11,15], target = 9 Output: [0,1] Output: Because nums[0] + nums[1] == 9, we return [0, 1]. my code is: /** * Note: The returned array must be malloced, assume caller calls free(). */ int* twoSum(int* nums, int numsSize, int target, int* returnSize ..read more

I'm trying to validate a string that must only contain ASCII visible characters, white space and \t. But it seems that ASCII table lookups are faster than the _mm_cmpestri instruction with _SIDD_CMP_RANGES on most CPUs. I've tested it on an i5-2410M, an i7-3720QM, an i7-5600U and a KVM-virtualized Xeon of unknown type and only on the last one is the vectorized version faster. My test code is here: #include <stdio.h> #include <string.h> #include <inttypes.h> #include <sys/time.h> #include <sys/mman.h> #include <immintrin.h> #include <stdalign.h> #inclu ..read more

I saw a common pattern when installing a C/C++ package from source on Linux (Ubuntu 16.04): ./autogen.sh ./configure make make install I understand make and make install, and I guess configure creates a Makefile based on user preferences, but I don't see why autogen.sh is necessary. Does anyone know what it is there for ..read more

I am writing a C daemon, which depends on the existence of two kernel modules in order to do its job. The program does not directly use these (or any other) modules. It only needs them to exist. Therefore, I would like to programmatically check whether these modules are already loaded or not, in order to warn the user at runtime. Before I start to do things like parsing /proc/modules or lsmod output, does a utility function already exist somewhere? Something like is_module_loaded(const char* name); I am pretty sure this has been asked before. However, I think I am missing the correct terms to ..read more

I'm trying to compile the sorting library from http://www.yendor.com/programming/sort/ Direct Link to library: http://www.yendor.com/programming/sort/sort-all.tgz When I run make the compiler says: gcc -g -O -DCUTOFF=15 -c sorttest.c In file included from sorttest.c:15: sort.h:66: error: conflicting types for ‘heapsort’ /usr/include/stdlib.h:301: error: previous declaration of ‘heapsort’ was here make: *** [sorttest.o] Error 1 Can someone help with this issue ..read more