Recent questions tagged C

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c - GCC: Array type has incomplete element type

I have declared a struct, and I try to pass an array of those structs (as well as a double array of doubles, ... ], but I get the same thing. 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 - printf string, variable length item

#define SIZE 9 int number=5; char letters[SIZE]; /* this wont be null-terminated */ ... char fmt_string[20]; ... there a better way to do 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 - undefined reference when calling inline function

I am getting a really odd error from GCC 4.8.1 with inline functions. I have two near-identical inline ... headers (i.e. not prototyped) 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 could I intercept linux sys calls?

Besides the LD_PRELOAD trick , and Linux Kernel Modules that replace a certain syscall with one provided by you , ... reaches the actual open ? 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 - Read from file or stdin

I am writing a utility which accepts either a filename, or reads from stdin. I would like to know the most robust ... | myprog Size of stdin: -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 - Parse string into argv/argc

Is there a way in C to parse a piece of text and obtain values for argv and argc, as if the text had ... don't care about quoting 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 - Returning pointer from a function

I am trying to return pointer from a function. But I am getting segmentation fault. Someone please tell what is ... point=12; return point; } 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 find largest triangle in convex hull aside from brute force search

Given a convex polygon, how do I find the 3 points that define a triangle with the greatest area. Related: ... bounding circle of the polygon? 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 popen() make bidirectional pipes like pipe() + fork()?

I'm implementing piping on a simulated file system in C++ (with mostly C). It needs to run commands in the ... 'r+' for reading and writing. 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 - Determining sprintf buffer size - what's the standard?

When converting an int like so: char a[256]; sprintf(a, "%d", 132); what's the best way to determine ... way of determining that on the fly? 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 - malloc implementation?

I'm trying to implement malloc and free for C, and I am not sure how to reuse memory. I currently have a ... of confused how to implement 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 - gcc, strict-aliasing, and casting through a union

Do you have any horror stories to tell? The GCC Manual recently added a warning regarding -fstrict-aliasing and ... rules for the example 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 - Is there any overhead for using variable-length arrays?

Is there some overhead of using variable-length arrays? Could the size of array be passed via command line ... dynamically allocating an 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 - Why doesn't GCC optimize structs?

Systems demand that certain primitives be aligned to certain points within the memory (ints to bytes that are ... which I am oblivious). 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 snprintf() ALWAYS null terminating?

Is snprintf always null terminating the destination buffer? In other words, is this sufficient: char dst[10]; ... is not standard behavior. 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 unsigned datatype?

I've seen this unsigned "typeless" type used a couple of times, but never seen an explanation for it. I ... , or just a compiler extension? 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 do I get a warning every time I use malloc?

If I use malloc in my code: int *x = malloc(sizeof(int)); I get this warning from gcc: new.c:7 ... declaration of built-in function malloc' 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 print a non-null-terminated string using printf?

How can I print a non-null-terminated string using printf, assuming that I know the length of the string 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 - Time complexity of a recursive algorithm

How can I calculate the time complexity of a recursive algorithm? int pow1(int x,int n) { if(n==0){ return 1; } else ... n/2) return p * 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 - After forking, are global variables shared?

Consider this simple code: int myvar = 0; int main() { if (fork()>0) { myvar++; } else { // ... value shared with the father (like pthread)? 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 print uint32_t and uint16_t variables' value?

I am trying to print an uint16_t and uint32_t value, but it is not giving the desired output. #include <stdio. ... will be the desired output? 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 wrap printf() into a function or macro?

This might sound like an interview question but is actually a practical problem. I am working with an embedded ... macros for numerous reasons. 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 - How to check if a given file descriptor stored in a variable is still valid?

I have a file descriptor stored in a variable say var. How can I check whether that descriptor is valid at a later ... . Any API's for that ? See Question&Answers more detail:os...

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

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271 views

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c - Dynamically create an array of strings with malloc

I am trying to create an array of strings in C using malloc. The number of strings that the array will hold can ... ], string2); /* etc */ 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 is printf with a single argument (without conversion specifiers) deprecated?

In a book that I'm reading, it's written that printf with a single argument (without conversion specifiers ... . What are these vulnerabilities? 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 nth byte of integer

I know you can get the first byte by using int x = number & ((1<<8)-1); or int x = number & 0xFF; But ... be 4 and the last two would be 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 - I'm trying to understand getchar() != EOF

I'm reading The C Programming Language and have understood everything so far. However when I came across the ... book and become more confused. See Question&Answers more detail:os...

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

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720 views

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c - Why is matrix multiplication faster with numpy than with ctypes in Python?

I was trying to figure out the fastest way to do matrix multiplication and tried 3 different ways: Pure python ... it is kind of obvious. See Question&Answers more detail:os...

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

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