Recent questions tagged C

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c - If free() knows the length of my array, why can't I ask for it in my own code?

I know that it's a common convention to pass the length of dynamically allocated arrays to functions that ... har-har) knowledge from? 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 - Is it guaranteed to be safe to perform memcpy(0,0,0)?

I am not so well-versed in the C standard, so please bear with me. I would like to know if it is ... that the memory regions overlap 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 - dynamic allocation/deallocation of 2D & 3D arrays

I know about algorithms to allocate/deallocate a 2D array dynamically, however I'm not too sure about the same for 3D ... ]); } free(arr3D); } 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 - MPI_Type_create_subarray and MPI_Gather

I have to solve a little mpi problem. I have 4 slaves processes and each of these wants to send a 2d subarray ( ... MPI. return 0; } Thanks all. 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 does srand relate to rand function?

I understand that rand() function generates the same number(s) each you run it if you don't change the ... srand is called first before rand? 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 socket to network interface

How can I bind a socket to a particular network interface? I tried using setsockopt on server side, but the ... mentioning the IP address). 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 does request_mem_region() actually do and when it is needed?

I'm studying on writing embedded linux driver, and decided to fire a few GPIOs to make sure I understand the ... ()? Thanks for any replies! 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 real difference between Pointers and References?

AKA - What's this obsession with pointers? Having only really used modern, object oriented languages like ActionScript ... missing out on 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 - How do *nix pseudo-terminals work ? What's the master/slave channel?

I want to write a simple, dumb, X terminal emulator in C on a Linux system. At first, I just thought I would ... } close(master); return 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 to make gcc link strong symbol in static library to overwrite weak symbol?

My problem can be summarised in the following: bar.c: #include <stdio.h> void bar() { printf("bar "); ... the weak symbol in main.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 - Query on -ffunction-section & -fdata-sections options of gcc

The below mentioned in the GCC Page for the function sections and data sections options: -ffunction-sections -fdata ... Am I missing something? 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 flush the CPU cache for a region of address space in Linux?

I am interested in flushing cache (L1, L2, and L3) only for a region of address space, for example all ... either from user or kernel space? 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 resolve the "EVP_DecryptFInal_ex: bad decrypt" during file decryption

I have the following query.Could any one please suggest me a solution. I'm working on encryption and decryption of ... return 0; } Thank you. 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 realloc and memcpy work?

I have two questions. Do realloc() and memcpy() copy the entries in an array to another in a way faster ... decreasing the size of the array ? 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 - Can I do a copy-on-write memcpy in Linux?

I have some code where I frequently copy a large block of memory, often after making only very small changes to ... it and doing it myself. 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 - Where can I find system call source code?

In Linux where can I find the source code for all system calls given that I have the source tree? ... type in terminal like my_system_call? 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 scanf() and fgets()

I want to know what is the difference between fgets() and scanf(). I am using C as my platform. 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 - getopt does not parse optional arguments to parameters

In C, getopt_long does not parse the optional arguments to command line parameters parameters. When I run the program, the ... } } return 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 get the keyboard state in Linux?

I want to check if the user pressed down the Shift key when the program starts. (That means, press ... with accessing the terminal directly. 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 - size of a datatype without using sizeof

I have a data type, say X, and I want to know its size without declaring a variable or pointer of that ... work with user defined data type. 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 exactly does fork return?

On success, the PID of the child process is returned in the parent's thread of execution, and a 0 is returned in the ... is p equal to 0 or PID? 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 - UDP Socket Set Timeout

I am trying to set a 100ms timeout on a UDP Socket. I am using C. I have posted relavent pieces of my code ... %d ", seq_num); num_timeouts++; } 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 - Can you bind() and connect() both ends of a UDP connection

I'm writing a point-to-point message queue system, and it has to be able to operate over UDP. I could ... nicely symmetric way to do it. 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 - Check if process exists given its pid

Given the pid of a Linux process, I want to check, from a C program, if the process is still running. 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's sizeof(size_t) on 32-bit vs the various 64-bit data models?

On a 64-bit system, sizeof(unsigned long) depends on the data model implemented by the system, for example, ... 64-bit data models on Wikipedia See Question&Answers more detail:os...

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

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491 views

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c - Using realloc to shrink the allocated memory

Simple question about the realloc function in C: If I use realloc to shrink the memory block that a pointer is ... Will I have a memory leak? See Question&Answers more detail:os...

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

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301 views

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c preprocessor - C++ #include semantics

This is a multiple question for the same pre-processing instruction. 1 - <> or "" ? Apart from the info found ... ) and what are the pros/cons? 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 - Dereferencing type-punned pointer will break strict-aliasing rules

I used the following piece of code to read data from files as part of a larger program. double data_read( ... example with the real function. See Question&Answers more detail:os...

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

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