Recent questions tagged C

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c - how to take integers as command line arguments?

I've read a getopt() example but it doesn't show how to accept integers as argument options, like cvalue would ... or something, not sure... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How does the gcc `__thread` work?

How is __thread in gcc implemented? Is it simply a wrapper over pthread_getspecific and pthread_setspecific? With my ... a quite big rewrite. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Where are the symbols etext, edata and end defined?

This is a code from Linux man page: #include <stdio.h> #include <stdlib.h> extern char etext, edata, end; ... it by linker or something else ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Do compilers produce better code for do-while loops versus other types of loops?

There's a comment in the zlib compression library (which is used in the Chromium project among many others) ... of context in the comments. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What is the fastest way to return the positions of all set bits in a 64-bit integer?

I need a fast way to get the position of all one bits in a 64-bit integer. For example, given x = 123703, I' ... 131.96s 44.55s 44.51s 11.58s See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How to disable compiler optimizations in gcc?

I am trying to learn assembly language. I have searched and found how to disassemble a .c file but I think ... which corresponds to my C file. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How to sort a stack using only stack operations?

I found this question on the web. Given a stack S, write a C program to sort the stack (in the ascending ... What is optimal solution to this? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Where is ssize_t defined in Linux?

OS: Debian 9 (Linux 4.9) Compiler: GCC 8.2 Currently I am including <stddef.h> (where size_t is defined) ... have ssize_t. Where is it defined? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What is intptr_t,is it a type for integer or pointer?

It's defined in /usr/include/stdint.h: typedef long int intptr_t; is it supposed to be a type for integer or pointer? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Incompatible pointer types and constness

I have a function taking a static two-dimensional array and treating the elements of the elements of the ... pointers/arrays be incompatible? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Using '__progname' instead of argv[0]

In the C / Unix environment I work in, I see some developers using __progname instead of argv[0] for usage messages ... argv[0]. Is it portable? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Is recent GTK 3.22 still Boehm GC friendly (thread issue)?

The Boehm's conservative garbage collector is quite useful (e.g. Bigloo is using it, Guile is ... by g_application_run via g_bus_get_sync See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Size of char pointer array from function

Using this code: #include <stdio.h> void printSize(char *messages[]) { printf("%d", sizeof(messages) / ... they are giving different results. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Any guarantees for uninitialised variables?

There are many claims that any use of uninitialised variables invokes undefined behavior (UB). Perusing the docs, I could ... format "%d" */ } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What is the behavior of scanf when using "%s" format specifier for reading in single char?

#include <stdio.h> int main(void){ char a; scanf("%s", &a); return 0; } Works for me, but I ... context there might be any unexpected results. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How do I get the number of members in a structure?

I want to count the number of members in a structure. For example: typedef struct { char MrChar; int ... NumberOfMem(&FooStr) should return 3 See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - fastest way to determine if a bit is set in a integer data type

I have a method that computes a hash value as per some specific algorithm. uint8_t cal_hash(uint64_t _in_data) { ... Anything better than this ? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Non-static variable initialization

I'm reading a book C progaming faq's. Here is passage of the book Automatic variables are variables defined ... Why is the variable initialized? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - The neighbors in Gray code

Is there any algorithm that I can use to find the neighbors in Gray code? For small numbers is just fine to ... grey code table with 6 numbers. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - malloc-ating multidimensional array in function

I'm trying to allocate a 2d array in a C program. It works fine in the main function like this (as ... correctly to the function. Many thanks. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How void pointer arithmetic is happening in GCC

int main() { int a; void *p; p = &a; printf("%ld ",(long)p); p = p+1; printf("%ld ", ... pointer, if it is implicitly doing pointer arithmetic. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Can someone please explain how stdio buffering works?

I don't understand what the buffer is doing and how it's used. (Also, if you can explain what a buffer normally does) ... too. "); exit(0); } See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How to handle buffering serial data

I am trying to figure out a nice solution to reading serial data, and what to do when a read() is ... process_message(); int remove_message(); See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Building CUnit on Windows

Has anyone managed to build the CUnit library for Windows? I want to run the same unit tests under ... - any assistance gratefully receveived See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - casting sockaddr_storage as sockaddr_in for inet_ntop

I am trying to cast a sockaddr_storage to a sockadd_in, so that i can print out the source ip address of ... understand where i am going wrong. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - read() from stdin doesn't ignore newline

I am using the following conditional statement to read from standard input. if ((n = read(0,buf,sizeof(buf) ... from standard input (stdin)? See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Count the number of occurrences of each letter in string

How can I count the number of occurrences in c of each letter (ignoring case) in the string? So that it would print out ... b : 0 c : 2 etc... See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Is it a better practice to typecast the pointer returned by malloc?

For the C code below, compare the defintions of the int pointers a and b; #include <stdio.h> #include <stdlib ... left hand side, applies here. See Question&Answers more detail:os...

asked Oct 24, 2021 in Technique[技术] by 深蓝 (71.8m points)

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