Recent questions tagged c

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c - What does the FD_CLOEXEC fcntl() flag do?

Like so: if (fcntl(fd, F_SETFD, FD_CLOEXEC) == -1) { ... Though I've read man fcntl, I can't figure out what it does. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Pipe buffer size is 4k or 64k?

I read in multiple places that the default buffer size for a pipe is 4kB (for instance, here), and my ulimit ... 64k! What is happening here?? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Stack variables vs. Heap variables

Am I correct in thinking that: char *buff[500]; ... creates a stack variable, and: char *buff = (char * ... function a stack frame on the stack? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How to repeat a char using printf?

I'd like to do something like printf("?", count, char) to repeat a character count times. What is the right ... is just what I wanted to avoid. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - close() is not closing socket properly

I have a multi-threaded server (thread pool) that is handling a large number of requests (up to ... inappropriately by multiple threads. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Working of __asm__ __volatile__ ("" : : : "memory")

What basically __asm__ __volatile__ () does and what is significance of "memory" for ARM architecture? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Bind failed: Address already in use

I am attempting to bind a socket to a port below: if( bind(socket_desc,(struct sockaddr *) &server, sizeof( ... use Why does this error occur? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - strcpy vs strdup

I read that strcpy is for copying a string, and strdup returns a pointer to a new string to duplicate the ... do you prefer to use strdup? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Linking against older symbol version in a .so file

Using gcc and ld on x86_64 linux I need to link against a newer version of a library (glibc 2.14) but ... which might be useful sometimes too. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Regular expression for a string literal in flex/lex

I'm experimenting to learn flex and would like to match string literals. My code currently looks like: """ ... with flex. Please advise! See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Strings and character with printf

I was confused with usage of %c and %s in the following C program #include <stdio.h> void main() { char name[] ... argument 2 has type char *' See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Convert a Static Library to a Shared Library?

I have a third-party library which consists mainly of a large number of static (.a) library files. I can compile ... into a single .so file? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Initializing a struct to 0

If I have a struct like this: typedef struct { unsigned char c1; unsigned char c2; } myStruct; What would be the ... ? myStruct _m2 = {0,0}; See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How can I convert a file pointer ( FILE* fp ) to a file descriptor (int fd)?

I have a FILE *, returned by a call to fopen(). I need to get a file descriptor from it, to make ... a file descriptor from a file pointer? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Measuring Cache Latencies

So I am trying to measure the latencies of L1, L2, L3 cache using C. I know the size of them and I feel I ... 0 0 0 0 1 0 0 clock_gettime(CLOCK_REALTIME, &endAccess); //e...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - faster equivalent of gettimeofday

In trying to build a very latency sensitive application, that needs to send 100s of messages a seconds, ... 62 nanoseconds gettimeofday takes See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Socket accept - "Too many open files"

I am working on a school project where I had to write a multi-threaded server, and now I am comparing it to ... to help. Any way around this? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Explain this implementation of malloc from the K&R book

This is an excerpt from the book on C by Kernighan and Ritchie. It shows how to implement a version of malloc. Although ... = bp; freep = p; } See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Function pointers, Closures, and Lambda

I am just now learning about function pointers and, as I was reading the K&R chapter on the subject, the first ... the two so closely. Thanks. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Freaky way of allocating two-dimensional array?

In a project, somebody pushed this line: double (*e)[n+1] = malloc((n+1) * sizeof(*e)); Which ... we'd use something we actually understand. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What is the difference between memmove and memcpy?

What is the difference between memmove and memcpy? Which one do you usually use and how? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - How do I gaussian blur an image without using any in-built gaussian functions?

I want to blur my image using the native Gaussian blur formula. I read the Wikipedia article, but I am not ... in functions like what MATLAB has See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - What is the difference between a Linux platform driver and normal device driver?

Earlier I had assumed that : Platform driver is for those devices that are on chip. Normal device driver ... devices. Please somebody explain. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Buffer overflow works in gdb but not without it

I am on CentOS 6.4 32 bit and am trying to cause a buffer overflow in a program. Within GDB it works. Here ... it seg faults. Why might this be? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Difference between fprintf, printf and sprintf?

Can anyone explain in simple English about the differences between printf, fprintf, and sprintf with examples? What ... File Handling in C". See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Printing all global variables/local variables?

How can I print all global variables/local variables? Is that possible in gdb? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - Writing and reading (fwrite - fread) structures with pointers

I'm working on a mailbox project, and I have these two structures: struct mmbox_mail struct mmbox_mail { char * ... , one inside one other. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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c - segmentation fault using scanf with integer

I am getting a segmentation fault in my C code when trying to read integer input from the user with the following ... ) from /lib64/libc.so.6 See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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