Recent questions tagged C

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c - Argument conversion: (normal) pointer to void pointer, cast needed?

When assigning to or from a void-pointer no cast is needed (C99 §6.3.2.2 sub 1 / §6.5.16.1 sub 1) ... to a function that expects a void-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 - Reversing words in a sentence

I'm currently going through K.N. King's C Programming: A Modern Approach. I've made it past the text for the ... } Output: http://drp.ly/1nYt5J 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 execute a command as root

I develop a C code on Linux (Debian). Time to time, I need to execute some commands through system() I wonder if ... I can use on the C code? 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 OPENSSL_cleanse look so complex and thread-unsafe?

This is the implementation of OPENSSL_cleanse in OpenSSL 1.0.1i unsigned char cleanse_ctr = 0; void OPENSSL_cleanse(void ... data race in 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 - is char signed or unsigned by default on iOS?

Is char signed or unsigned by default on iOS? (I thought this would've been a well answered question, but oddly ... up nothing at all useful!) 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 "representable" mean in C11?

According to C11 WG14 draft version N1570: The header <ctype.h> declares several functions useful for ... it is implementation-defined. 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 - gcc complains: variable-sized object may not be initialized

I've looked at these and they do not answer my question: variable-sized object may not be initialized C compile error: " ... int bar[foo]={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 - List of locales in Windows

On *nix systems you can do locale -a to get a list of available locales. What is the equivalent ... force guessing Windows locale names. 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 - Unroll loop and do independent sum with vectorization

For the following loop GCC will only vectorize the loop if I tell it to use associative math e.g. with -Ofast. float ... ..B1.8 # Prob 99% #5.3 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 - sizeof array clarification

I am studying for a final tomorrow in C, and have a question regarding the sizeof operator. Let's say the size of ... to how large zap may 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 - Arduino: printf/fprintf prints question mark instead of float

I have the following code for an Arduino sketch: #include <LiquidCrystal.h> LiquidCrystal lcd(12, 11, 5, 4, 3, ... Any idea what's the problem ? 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 this program print "forked!" 4 times?

Why does this program print forked! 4 times? #include <stdio.h> #include <unistd.h> int main(void) { fork() && ... ("forked! "); 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 - Linux process stack overrun by local variables (stack guarding)

From What is the purpose of the _chkstk() function?: At the end of the stack, there is one guard page ... the assembly code is compiler-related. 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 happens to memory after free()?

I know that on your hard drive, if you delete a file, the data is not (instantly) gone. The data is still ... free() it until it is overwritten? 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 comma operator work during assignment?

int a = 1; int b = (1,2,3); cout << a+b << endl; // this prints 4 Is (1,2,3) some ... the compiler simply take the last value from the list? 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 - Struct pointer compatibility

Suppose we have two structs: typedef struct Struct1 { short a_short; int id; } Struct1; typedef struct Struct2 { ... compiler flag? 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 - fscanf return value

What does fscanf return when it reads data in the file. For example, int number1, number2, number3, number4, c ... on the number of arguments. 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 can the execve system call run "/bin/sh" without any argv arguments, but not "/bin/ls"?

I am confused with the syscall of __NR_execve. When I learn linux system call. The correct way that I know to use ... while "/bin/ls" fail? 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 - Do math functions of constant expressions get pre-calculated at compile time?

I tend to use math functions of constant expressions for convinience and coherence (i.e log(x)/log(2) ... be wastefully calculated at runtime? 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 - Avoid Overflow when Calculating π by Evaluating a Series Using 16-bit Arithmetic?

I'm trying to write a program that calculates decimal digits of π to 1000 digits or more. To practice low ... understand the long context 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 - What float value makes sprintf_s() produce "1.#QO"?

I have some (legacy embedded c) code which produces a .csv file by means of some sprintf calls. ... Microsoft-specific representation of NaN? 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 there a Python constant for Unicode whitespace?

The string module contains a whitespace attribute, which is a string consisting of all the ASCII characters ... specifically about a constant. 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 - Get directory separator char on Windows? ('', '/', etc.)

tl;dr: How do I ask Windows what the current directory separator character on the system is? Different versions of ... people get what I meant.) 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 - Structs that refer to each other

I want to have two structs that can contain each other. Here is an example: struct a { struct b bb; }; ... Is there a way to achieve 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 - segmentation fault(core dumped) error while using inline assembly

I'm using inline assembly in GCC. I want to rotate a variable content 2 bits to the left (I moved the variable to the ... ("%" PRIu64 " " , X); 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 perform reduction on a huge 2D matrix along the row direction using cuda? (max value and max value's index for each row)

I'm trying to implement a reduction along the row direction of a 2D matrix. I'm starting from a code I found on ... ",max_val[z]); 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 - Python memory model for this program

My query is on the below program with respect to symbols that are storing values and functions, when ran on ... pointing to function sub()? 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 calculate size of array from pointer variable?

i have pointer of array(array which is in memory). Can i calculate the size of array from its pointer ? i ... to calculate array size. 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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