Recent questions tagged c

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c - what does the -p and -g flag in compiler

I have been profiling a C code and to do so I compiled with -p and -g flags. So I was wandering what do ... do they add to the binary? 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 - Conversion of integer pointer to integer

Tried following code to check what happens when we convert integer pointer to a integer . #include<stdio.h> ... topic would also be helpful. 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 - read before write is undefined with malloced memory?

According to this reddit comment thread, it is undefined if an attempt is made to read memory before it has been ... more light on this issue. 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 - Opening a file in 'a+ 'mode

If a file is opened using the following command: FILE *f1=fopen("test.dat","a+"); The man page reads: a+ ... one for read & another for write? 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 do unsigned "small" integers promote to signed int?

The standard is clear: when performing arithmetic on an integral type smaller than int, the integer is first ... opinion-based" speculation. 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 number of cores in Win32?

I'm writing a program in C on windows that needs to run as many threads as available cores. But I dont know ... the number of cores. Any ideas? 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 - Can I name a variable with the same name as a typedef'd structure name?

Here is the structure declare code. struct list_el { int val; struct list_el * next; }; typedef struct list_el item ... code can't be compiled? 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 - Memory allocated with alloca gets freed at end of function or at end of scope?

If I have a function like this: void bla(int size) { while(b){ char tmp[size]; ...... } } tmp gets ... at end of scope or at end of 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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c - Incrementing function pointers

I just learned about function pointers (pointers pointing at the adress where where the machine code of a function is ... or am I way off? 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 - Printing unsigned long long int Value Type Returns Strange Results

I have a problem while using the printf function to print values of type unsigned long long int I have no idea ... Could you explain it to me? 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 define a macro to a function with the same name?

I found the code below in https://github.com/torvalds/linux/blob/master/arch/x86/include/asm/atomic.h static ... it necessary to do so? 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 -Wcast-align not warn about cast from char* to int* on x86?

I understand that gcc has an option -Wcast-align which warns whenever a pointer is cast such that the required ... 'm compiling it for x86? 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 - Make gdb quit automatically on successful termination?

I use a debugging script that runs several related processes in succession with the debugger. I'm currently using ... if level >= WARNING 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 - Write program that pretends to be a TTY

I'm writing a program that reads input from stdin, manipulates the input, and writes output to stdout. However, ... something I'm looking 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 - Is the array to pointer decay changed to a pointer object?

int a[] = {1, 2 ,3}; I understand that array names are converted to pointers. A term often used is ... memory or it's an implicit conversion? 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 `execvp` take a `char *const argv[]`?

I'm wondering if there is a reason between two exec functions differing in const-ness, of if this is just a ... do either of the above changes. 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 doesn't GCC optimize this call to printf?

#include <stdio.h> int main(void) { int i; scanf("%d", &i); if(i != 30) { return(0); } printf("i ... .3.1), or on 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 - How to check if float can be exactly represented as an integer

I'm looking to for a reasonably efficient way of determining if a floating point value (double) can be ... representable as a long? 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 - Are strtol, strtod unsafe?

It seems that strtol() and strtod() effectively allow (and force) you to cast away constness in a string: ... ) Isn't that really dangerous? 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 undefined behaviour to memcpy from an uninitialized variable?

Is using an uninitialized variable as the src for memcpy undefined behaviour in C? void foo(int *to) { int from; ... , &from, sizeof(from)); } 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 calling printf with excess arguments undefined behaviour?

I wonder if this yields in undefined behaviour: printf("Test %d %s", 123, "abc", "def", "ghi"); The first ... should be no UB. Is this correct? 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 - Will a void* always have the same representation as a char*?

Will a void* always have the same representation as a char* ? Details: I want to work with a variadic function that ... my variadic(char*,...)? 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 - Assembly code fsqrt and fmul instructions

I'm trying to compute 1.34 *sqrt(lght) in this function using inline assembly but I'm getting errors like: ' ... using Ubuntu so GCC, 32 bits 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 does in assembly does assigning negative number to an unsigned int work?

I Learned About 2's Complement and unsigned and signed int. So I Decided to test my knowledge , as far ... not find a satisfactory 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 - What is signed integer overflow?

I'm learning C from CS50. When I run my code, it says 'signed integer overflow'. #include <stdio.h> ... Can someone explain what that means? 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 - Segmentation Fault doesn't come up immediately after accessing out-of-bound memory

I wrote this piece of code and was expecting a segmentation fault quicly, but it seems I am allowed to access ... anything... Thanks, bests. 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 is Memory Allocated to variables of different data types?

I wrote the following Code. #include<stdio.h> int main() { int x = 1 ; int *j = &x ; int y ... pointer value as suggested by Keith Thompson. 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 we do not use '&' in scanf for char arrray

int age; char name[10]; scanf("%d", &age); scanf("%s", name); In first scanf function we use '&' symbol ... . Can anybody tell me why is so? See Question&Answers more detail:os...

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

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