Recent questions tagged C

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c - Warning: array subscript has type char

When I am running this program I am getting warning "array subscript has type 'char'". Please help me where is it ... } main() { NoFive(); } 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 - Compiler not detecting obviously uninitialized variable

All C compilers I've tried won't detect uninitialized variables in the code snippet below. Yet the case is ... + 2013 with all warnings enabled 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 the compare function in qsort work?

I found this sample code online, which explains how the qsort function works. I could not understand what the compare ... ); } 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 - Copying content from a hidden or clipped window in XP?

I need to copy the content of a window (BitBlt) which is hidden, to another window. The problem is that once I ... I got isn't painted anymore. 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 - Defined behaviour for expressions

The C99 Standard says in $6.5.2. Between the previous and next sequence point an object shall have its stored value modified ... + or a[i] = 1? 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 - whitespace in the format string (scanf)

Consider the following code: #include<stdio.h> int main() { int i=3, j=4; scanf("%d c %d",&i,&j); printf(" ... and vice versa if it is %d c %d? 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't step into string.h function with GDB

Having trouble stepping into string.h in GDB 7.5. Here's a simple example program: Source code: #include <stdio ... no such file or directory. 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 - Macro and function with same name

I have the following code #define myfunc(a,b) myfunc(do_a(a), do_b(b)) void myfunc(int a, int b) ... I can't change function implementation. 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 possible to call a non-exported function that resides in an exe?

I'd like to call a function that resides in a 3rd-party .exe and obtain its result. It seems like there ... -installed so my software will run. 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 set close-on-exec by default

I'm implementing a library to run commands. The library is C, on Linux. It currently does a popen() call ... default for the process? 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 - Why does my compiler not accept fork(), despite my inclusion of <unistd.h>?

Here's my code (created just to test fork()): #include <stdio.h> #include <ctype.h> #include <limits.h> ... 'fork' What is wrong with 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 - Executing shell script with system() returns 256. What does that mean?

I've written a shell script to soft-restart HAProxy (reverse proxy). Executing the script from the shell works. ... run with sudo. Any hints? 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 many chars can be in a char array?

#define HUGE_NUMBER ??? char string[HUGE_NUMBER]; do_something_with_the_string(string); I was wondering what would be ... the maximum possible. 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 - Sharing memory between processes through the use of mmap()

I'm in Linux 2.6. I have an environment where 2 processes simulate (using shared memory) the exchange of data ... this path. Thanks in advance! 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 sprintf(buffer, "%s […]", buffer, […]) safe?

I saw use of this pattern to concatenate onto a string in some code I was working on: sprintf(buffer, "%s <input ... ", id); to replace 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 - Is the integer constant's default type signed or unsigned?

Is the integer constant's default type signed or unsigned? such as 0x80000000, how can I to decide to use it as a ... 3); output: n>>3: f0000000 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 - flock(): removing locked file without race condition?

I'm using flock() for inter-process named mutexes (i.e. some process can decide to hold a lock on ... without introducing this race condition ? 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 - Equivalents to MSVC's _countof in other compilers?

Are there any builtin equivalents to _countof provided by other compilers, in particular GCC and Clang? Are there any non-macro forms? 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 is sleep implemented at the OS level?

I am just interested how sleep(time in ms) is implemented in a C library or basically at the OS level... ... "sleep()" function is implemented. 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 we check if a pointer is NULL pointer?

I always think simply if(p != NULL){..} will do the job. But after reading this Stack Overflow question, ... pointers can have non-zero value? See Question&Answers more detail:os...

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

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703 views

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c - Pipes, dup2 and exec()

I have to write a shell that can run pipes. For example commands like ls -l | wc -l". I have ... up right after I enter the command? See Question&Answers more detail:os...

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

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329 views

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c - When printf is an address of a variable, why use void*?

I saw some usage of (void*) in printf(). If I want to print a variable's address, can I do it like this: int ... )? Can't I use (int)&a instead? 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 get the value of individual bytes of a variable?

I know that to get the number of bytes used by a variable type, you use sizeof(int) for instance. How do you get the ... ? (i.e. int x = 125.) 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 - /proc/[pid]/pagemaps and /proc/[pid]/maps | linux

I'm trying to get my head around the two files mentioned in the title. I've looked up what the bits are; ... doesn't persist in a 32bit OS. 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 - Problems with SO_BINDTODEVICE Linux socket option

I have a PC with two network cards. One (eth0) is for LAN/internet and the other for UDP communication with ... EXIT_FAILURE); } return(rc); } See Question&Answers more detail:os...

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

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584 views

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c - Is there a better way than parsing /proc/self/maps to figure out memory protection?

On Linux (or Solaris) is there a better way than hand parsing /proc/self/maps repeatedly to figure out ... pretty much anything in /proc) 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 - Should variable definition be in header files?

My very basic knowledge of C and compilation process has gone rusty lately. I was trying to figure out ... multiple definitions of the symbol? See Question&Answers more detail:os...

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

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399 views

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c - How to check heap size for a process on Linux

I was writing some code and it kept crashing. Later after digging the dumps I realized I was overshooting the ... reply is unclear to me. See Question&Answers more detail:os...

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

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