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Questions tagged [c-standard-library]

The C standard library is the standard library for the C programming language, as specified in the ANSI C standard

The C standard library is the standard library for the C programming language, as specified in the ANSI C standard. It was developed at the same time as the C POSIX library, which is a superset of it. Since ANSI C was adopted by the International Organization for Standardization, the C standard library is also called the ISO C library.

The C standard library provides macros, type definitions, and functions for tasks like string handling, mathematical computations, input/output processing, memory allocation and several other operating system services.

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Difference between C standard library and C POSIX library

I'm a little confused by "C standard lib" and "C POSIX lib", because I found that, many header files defined in "C POSIX lib" are also part of "C standard lib". So, I assume that, "C standard lib" is a lib defined by ANSI C organization, and there…
Alcott
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Why wasn't a specifier for `float` defined in `printf`?

It looks like it could have been, there are (at least in C99) length modifiers that can be applied to int: %hhd, %hd, %ld and %lld mean signed char, short, long and long long. There is even a length modifier applicable to double: %Lf means long…
skyking
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Why do some built-in Python functions only have pass?

I wanted to see how a math.py function was implemented, but when I opened the file in PyCharm I found that all the functions are empty and there is a simple pass. For example: def ceil(x): # real signature unknown; restored from __doc__ """ …
edgarstack
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Why isn't there int128_t?

A number of compilers provide 128-bit integer types, but none of the ones I've used provide the typedefs int128_t. Why? As far as I recall, the standard Reserves int128_t for this purpose Encourages implementations that provide such a type to…
user1084944
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What does the first "c" stand for in "calloc"?

A student asked the question and I didn't know for sure. Guesses include: "counted", "clearing", "chunked", "complete", ... The standard library documentation doesn't say what it stands for and there aren't similarly named functions that would…
Raymond Hettinger
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What's the meaning of "reserved for any use"?

NOTE: This is a c question, though I added c++ in case some C++ expert can provide a rationale or historical reason why C++ is using a different wording than C. In the C standard library specification, we have this normative text, C17 7.1.3…
Lundin
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what is difference between fgetpos/fsetpos and ftell/fseek

What's the difference between using the functions fgetpos() and fsetpos() and using the functions ftell() and fseek() to get and set a position in a file? What are fgetpos() and fsetpos() good for? Why would they be used instead of ftell() and…
carlfilips
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Does the C standard guarantee buffers are not touched past their null terminator?

In the various cases that a buffer is provided to the standard library's many string functions, is it guaranteed that the buffer will not be modified beyond the null terminator? For example: char buffer[17] = "abcdefghijklmnop"; sscanf("123",…
Segmented
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Why does pow(n,2) return 24 when n=5, with my compiler and OS?

#include #include #include int main() { int n,i,ele; n=5; ele=pow(n,2); printf("%d",ele); return 0; } The output is 24. I'm using GNU/GCC in Code::Blocks. What is happening? I know the pow function…
exsnake
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What is the difference between getch() and getchar()?

What is the exact difference between the getch and getchar functions?
bubble
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What standard C library does Clang use? glibc, its own, or some other one?

I'm pretty sure glibc is the name of the standard C library implementation for gcc. But for LLVM/Clang I'm not sure. I've Googled to try to find if it comes with its own implementation of the whole standard C library, or whether they also use glibc.…
hippietrail
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Why does fopen take a string as its second argument?

It has always struck me as strange that the C function fopen() takes a const char * as the second argument. I would think it would be easier to both read your code and implement the library if there were bit masks defined in stdio.h, like IO_READ…
Chris Cooper
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Advantages of strncmp over strcmp?

Seems strncmp is usually recommended than strcmp, what are the advantages? I think it could be related to security. If this is the case, is it still applicable if one of the input string is known to be literal constant, like…
Thomson
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why is abs() and fabs() defined in two different headers in C

The standard library function abs() is declared in stdlib.h, while fabs() is in math.h. Why are they reside in different headers?
Sanjana Jose
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"getenv... function ... may be unsafe" - really?

I'm using MSVC to compile some C code which uses standard-library functions, such as getenv(), sprintf and others, with /W3 set for warnings. I'm told by MSVC that: 'getenv': This function or variable may be unsafe. Consider using _dupenv_s…
einpoklum
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