Recent questions tagged C

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c - Finding common elements in two arrays of different size

I have a problem to find common elements in two arrays and that's of different size. Take , Array A1 of size ... know it's not a good solution. 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 - fopen() returning a NULL pointer, but the file definitely exists

The code I have is as follows: FILE *txt_file = fopen("data.txt", "r"); if (txt_file == NULL) { perror ... fopen() is returning a NULL 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 - AMD64 -- nopw assembly instruction?

In this compiler output, I'm trying to understand how machine-code encoding of the nopw instruction works: ... the Godbolt compiler explorer. 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 - (GCC) Dollar sign in printf format string

I've seen the following line in a source code written in C: printf("%2$d %1$d", a, b); What does it mean? 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 get current hour (time of day) in linux kernel space

I'm writing a kernel module that checks to see if the time is between two specified hours, and disables input ... in the current day. 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 - When zeroing a struct such as sockaddr_in, sockaddr_in6 and addrinfo before use, which is correct: memset, an initializer or either?

Whenever I look at real code or example socket code in books, man pages and websites, I almost always see ... , for reasons stated above. 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 difference between freeing the pointer and assigning it to NULL?

Could somebody tell me the difference between: int *p; p=(int*)malloc(10*sizeof(int)); free(p); or int *p; ... )malloc(10*sizeof(int)); p=NULL; 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 good practice to close file descriptors on exit

If for some reason, I discover a fatal situation in my program, and I would like to exit with an error ... closed when the process dies. 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 nfds from select() used for

I was wondering what the nfds does, after reading different manuals, I end up with the only answer being it is ... What is it exactly used for? 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 - Generating all distinct partitions of a number

I am trying to write a C code to generate all possible partitions (into 2 or more parts) with distinct ... a trivial but valid partition). 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 - Why does the doubly linked list in sys/queue.h maintain the address of previous next element?

I'm studying sys/queue.h from FreeBSD and I have one question: In sys/queue.h, LIST_ENTRY is defined as ... elment like struct type *le_prev? 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 - DYLD_LIBRARY_PATH & DYLD_INSERT_LIBRARIES not working

I create a .dylib file and compile it: #define _GNU_SOURCE #include <dlfcn.h> #include <stdio.h> static void ... .dylib A B C 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 - Double pointer vs array of pointers(**array vs *array[])

Im not clearly sure what is the difference between those 2. My professor wrote that **array is same as *array[] and ... ; freeAll(); return 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 - Why does malloc not work sometimes?

I'm porting a C project from Linux to Windows. On Linux it is completely stable. On Windows, it's working well ... ? What can I be doing 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 preprocessor - What do two adjacent pound signs mean in a C macro?

I'm taking a look at an application that defines a large set of constant arrays. What really confuses me is ... do those two pound signs mean? 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 does 'u' mean after a number?

Can you tell me what exactly does the u after a number, for example: #define NAME_DEFINE 1u 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 - parsing of mathematical expressions

(in c90) (linux) input: sqrt(2 - sin(3*A/B)^2.5) + 0.5*(C*~(D) + 3.11 +B) a b /*there are ... ,b,c,d is letters cos,sin,sqrt,ln is function*/ See Question&Answers more detail:os...

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

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682 views

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c - Building for MacOSX, but linking against dylib built for iOS Simulator file

I've just upgraded to Xcode 5 beta with the April 15 2013 commandline tools and hit the following warning when ... (. thanks for any help! 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 using a structure without all members assigned undefined?

Consider this code in block scope: struct foo { unsigned char a; unsigned char b; } x, y; x.a = 0; y = x ... is initialized, per 6.7.9 9.) 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 - Longest Common Subsequence for Multiple Sequences

I have done a bunch of research for finding the longest for M = 2 sequences, but I am trying to figure out ... 3 1 Expected output Length = 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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644 views

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c - Why do I need 17 significant digits (and not 16) to represent a double?

Can someone give me an example of a floating point number (double precision), that needs more than 16 significant ... this? Thanks a lot! See Question&Answers more detail:os...

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

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629 views

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c - What does signed and unsigned values mean?

What does signed mean in C? I have this table to show: This says signed char 128 to +127. 128 is also ... to the book Apress Beginning C. 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 copy one integer array to another

What is the best way to duplicate an integer array? I know memcpy() is one way to do it. Is there any function like strdup()? 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 - Why were bitwise operations slightly faster than addition/subtraction operations on older microprocessors?

I came across this excerpt today: On most older microprocessors, bitwise operations are slightly faster than addition ... of clock cycles. See Question&Answers more detail:os...

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

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883 views

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c - Differentiate VMware network adapter from physical network adapters -or- Detect Virtual Network Adaptor

I have to differentiate between the real addresses and the VM addresses using any Windows API. I'm using ... addresses and the real addresses. See Question&Answers more detail:os...

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

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656 views

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c - Use the same makefile for make (Linux) and nmake (Windows)

I have a simple C program (one source file) which I want to compile on Linux and on Windows via make ... what I'm trying absolutely impossible? See Question&Answers more detail:os...

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

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504 views

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c - What is the simplest RGB image format?

I am working in C on a physics experiment, Young's interference experiment and i made a program who prints to ... , 24bit RGB pixels Thank you. See Question&Answers more detail:os...

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

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636 views

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c - libc source location - for download or online viewing?

Sorry I know this is stupid but where is linux libc source code available? What I downloaded from GNU ... cross-referenced) version somewhere? See Question&Answers more detail:os...

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

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