Questions tagged [libc]

The C standard library consists of a set of sections of the ISO C standard which describe a collection of headers and library routines used to implement common operations, such as input/output and string handling, in the C programming language.

There are many implementations of libc with different resource requirements, security goals, etc. With a typical tool chain the libc, compiler and OS work together to achieve some ISO, Posix or custom features/standards. Some libc implementation are only a subset of the ISO standard, but still full featured enough to be used in many applications.

Specific libc tags:

glibc - the full Gnu Libc found on most GCC installs.
uclibc - a smaller micro-controller libc for resource constrained devices
bionic - Android libc
newlib - unhosted libc
musl - more modern lighter foot print libc

Websites

armcc (keil uVision4): how to get time() to return time from the RTC?

I'm a developer who's fairly used to working with embedded systems on Linux with free tools. Now I find myself on a project which uses the Keil compiler on Windows (armcc, uVision4... I'm finding the naming of stuff in this area a bit confusing…

time libc keil armcc

asked May 28 '12 at 08:48

Magnus

4,644
1
33
49

votes

1 answer

libc.so mmap strace

I am studying for exam tomorrow and I ran across this question: After we run an executable with strace the following syscalls result regarding standard C lib: open("/lib/libc.so.6", "O_RDONLY") = 3 mmap(NULL, 36803630, PROT_READ | PROT_EXEC,…

c mmap libc

asked May 25 '12 at 15:57

Dan Lincan

1,065
2
14
32

votes

1 answer

SIGSEGV backtrace with libc is repeating entries

I was using libunwind prior to moving to the available execinfo backtrace. After implementing a new backtrace I was enjoying it until I removed the libunwind from the project and did a full rebuild. Now my backtrace function refuses to produce a…

c++ c arm libc backtrace

asked May 18 '12 at 10:18

Ulterior

2,786
3
30
58

votes

1 answer

linking to libc on android/linux (x86) libc.so vs libc.so.6

I'm trying to build for an android device and I don't have real SDK/NDK for it. Unlike usual Android devices that have libc.so this one has symbolic link libc.so.6 --> libc-2.7.so. If I build with regular android NDK-x86 my shared lib (as reported…

android x86 libc

asked Apr 15 '12 at 02:38

Pavel P

15,789
11
79
128

-1

votes

1 answer

Why does the GNU coding standard prefer getopt_long over argp?

I do not understand why the GNU Coding Standard has the following line in Section 4.2 - Writing Robust Programs Use getopt_long to decode arguments, unless the argument syntax makes this unreasonable. My understanding is that getopt is part of the…

c gcc gnu libc getopt-long

asked Jul 15 '23 at 17:25

Scott Christensen

-1

votes

1 answer

ret2libc: sh: line 1: command not found

So I've been trying to develop a ret2libc exploit for my program as shown below: #include #include void vuln() { char arr[0x10]; scanf("%s", arr); printf("Input: %s",arr); } int main() { vuln(); return 0; } I've…

c buffer-overflow libc exploit

asked Apr 27 '23 at 22:20

bruh

-1

votes

1 answer

Meaning of the [k] symbol in perf report output

What is the meaning of the [k] symbol I can see in the following perf report output: + 63.93% 0.10% sample libc.so.6 [.] __GI___fstatat64 + 63.82% 63.82% sample [unknown] [k] 0xffffffffa90001a2 <----…

linux libc perf

asked Apr 09 '23 at 15:12

imrichardcole

4,633
3
23
45

-1

votes

1 answer

What are the differences between the various C standard library implementations

While I was researching how fopen and moreover the structure FILE are built I found out it wasn't all just GNU libc. I began to look closer at the various implementations such as Google's Bionic, Musl, Newlib and several others. Having only been…

c posix glibc libc ansi-c

asked Nov 10 '22 at 22:02

tijko

7,599
11
44
64

-1

votes

2 answers

How is a char array maximum size in C determined?

Learning C and checking the reference from the GNU reference manual. I don't understand how is the maximum size that can be allocated to a char array defined in an exact way. In my test program when the allocated size for a string array is "small"…

arrays c stack strtok libc

asked Sep 09 '22 at 18:15

varinme

-1

votes

1 answer

In which library write writev and other functions that operate on socket like send also and where is the location of .so file

I like to run this command to look for function names similar to sendfile, send, write writev on my some system library or kernel. command nm -D /usr/lib/libopenal.so.1 //or T option But I don't know where to look for these functions exact name the…

c linux shared-libraries glibc libc

asked Dec 18 '21 at 04:02

user786

3,902
4
40
72

-1

votes

2 answers

C++ print time difference?

In C++ I wrote: time_t tmp1, tmp2; time(&tmp1); sleep(1); time(&tmp2); std::cout << tmp2-tmp1; But every-time I run it I see 1 printed, why the result is too perfect? shouldn't it contain some milliseconds too?

c++ time libc

asked Jul 19 '21 at 01:03

user16468058

-1

votes

1 answer

How to let ld use PIC version of libc.a

To link gcc statically into a shared library, based on the answer in this question, the remaining problem is how to let the linker use the PIC version of libc.a instead of the non-PIC version. The problem is the same as that answer: g++ -fPIC -Wall…

c linker ld static-linking libc

asked Apr 23 '21 at 02:06

jw_

1,663
18
32

-1

votes

1 answer

Why does ISO/IEC 9899 not standardize the definitions of the functions in the C standard library?

ISO:IEC 9899 standardizes the prototypes of the functions of the C standard library and describes their behavior. It specifies the identifier, the return type and the parameter(s) with its matching type(s) of a certain C standard function. But why…

c function language-lawyer iso libc

asked Mar 17 '20 at 15:31

RobertS supports Monica Cellio

14,524
7
33
80

-1

votes

1 answer

How can I reset the environment to the default for a user when running program as that user?

I'm trying to run a program in Rust using libc as another user. nix::unistd::setuid(uid).unwrap(); If I fork and exec a process which runs printenv, the environment does not change. How can I reset the environment to the default for a user?

linux environment-variables language-agnostic libc

asked Mar 10 '20 at 20:23

Federico Ponzi

2,682
4
34
60

-1

votes

1 answer

Accidently renamed libc.so.6 and cannot chroot within rescue mode

We have accidently renamed shared library /lib64/libc.so.6 to be /lib64/libc.so_6. Right after previous command the system (CentOS 6.9) throws the following error : error while loading shared libraries: /lib64/libc.so.6: cannot open shared object…

libc chroot centos-6.9

asked Dec 11 '18 at 13:29

LiNuX

Prev 1 2 3

…

71 72 Next