This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Where to find stdio.h functions implementations ?
Hi, I am trying to find the function definitions of the functions defined in stdio.h header file, I want to learn how functions like printf() is achieved, but I can't find any preprocessor directives link in stdio.h to the implementation file elsewhere. How can a C Compiler know where to find the implementations when there are no direct references to the function definition file? (I learned that .h file may accompany with a same name .c implementation file from an objective-c book.) Could you help me? Thanks! I am using GCC on Mac OS X.
FreeBSD's libc is pretty well laid out in its src repository.
http://www.freebsd.org/cgi/cvsweb.cgi/src/lib/libc/
e.g. for printf(3):
http://svnweb.freebsd.org/base/head/lib/libc/stdio/printf.c?view=markup
http://svnweb.freebsd.org/base/head/lib/libc/stdio/vfprintf.c?view=markup
Try downloading source code for GLIBC library project. That's where definitions for standard functions are when using GCC compiler (and derivates).
Related
This question already has answers here:
difference between <stdlib.h> and <malloc.h>
(6 answers)
Closed 3 years ago.
A customer's code is expecting to find an include file malloc.h in one of the "usual suspect" locations. On my Mac, AFAICT, there is no malloc.h, at least not in any place you would expect to find it, such as /usr/include, /usr/local/include, or /opt/local/include. Since the malloc() is usually defined in stdlib.h, and since the code includes stdlib.h anyway, I was able to get the code to build by just commenting out the few includes of malloc.h. I am building with gcc.
But two questions: Is my gcc messed up somehow? Should that file be there? Also, the code bombs almost immediately with a seg fault that I haven't been able to track down yet. Could this be the consequence of using the wrong malloc()?
The malloc.h is deprecated and should not be used. It contains some non-standard functions too. If you want to use malloc, then include stdlib.h. Not even the C89 standard mentions malloc.h
If it's the cause of your problems, I don't know, but it's quite probable.
The listing below can provide ideas on where the file should/could be found. I can't explain the segfault without more details, though. I do not see how it could be related to malloc() in any way.
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/malloc.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/malloc/malloc.h
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/sys/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVOS.platform/Developer/SDKs/AppleTVOS.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchOS.platform/Developer/SDKs/WatchOS.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/sys/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX.sdk/System/Library/Frameworks/Kernel.framework/Versions/A/Headers/sys/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/WatchSimulator.platform/Developer/SDKs/WatchSimulator.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/AppleTVSimulator.platform/Developer/SDKs/AppleTVSimulator.sdk/usr/include/malloc/malloc.h
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator.sdk/usr/include/malloc/malloc.h
$
This question already has answers here:
How to embed version information into shared library and binary?
(4 answers)
Closed 6 years ago.
I have situation as below:
#define CONSTANT 123
foo()
{
...
}
Using the above code, after creating the library lets say test.so, how can get to know the CONSTANT macro value from the library? Is there any way?
You can define the constant in a header file and supply that header with the library.
There are ways to do that:
Define the constant in a header file to the library and distribute it with the library
Make the library some form of open source
Write a dedicated get_constant function that returns the value
Its worth noting that Macros are always sheer text replacement. So after compile time you won't even know they were there.
This question already has answers here:
Where are the functions in the C standard library defined?
(5 answers)
Closed 7 years ago.
Functions like printf() , scanf() , memset() , puts() etc have their declaration in header files but is there any mechanism to see the definition of these function..?
This might not be a new question but i could not find the appropriate solution for this.
Find your compilers include path (e.g. GCC solution)
Search for the header you are interested in (e.g. printf should be in stdio.h or more likely another header included by stdio.h)
Correctly configured, some IDEs will help you with that, e.g. Eclipse
The method has its limits though, because at some point the include files will get less and less Standard-C, but more and more compiler dependent. The C-standard does not prescribe the contents of standard headers. It merely states that if you write #include <stdio.h>, you can use printf(). That does not necessarily mean that stdio.h has some form you might expect.
This question already has answers here:
Why do you have to link the math library in C?
(14 answers)
Closed 9 years ago.
I'm confused why you have to type -lm to properly link math to your code, but don't have to do the same for stdio. I've only just started using C, so I apologize if this is a stupid quesiton or I'm missing something obvious.
In short, because of historical reasons,
The functions in stdio.h are in libc, while the functions in math.h are in libm. libc is linked by default but libm isn't.
There are two different things:
header files (stdio.h and math.h) - they contain only function prototypes and some definitions and data; they are #included in your source code
libraries (libm.so) - they contain binary code which will be linked back into your application (binary code). Also, for a library named libname.so the linker flag is -lname - for libm.so the flag is -lm.
Take also in consideration that there are libc.so and libstdc.so which are always linked into your application. Code for functions in stdio.h and stdlib.h and several others is found on those libraries - thus, it is always included.
PS: I'm assuming Linux/UNIX here, thus the names are very specific. On Windows things are similar but with other names (DLLs instead of .so files, etc.)
This question already has answers here:
Closed 11 years ago.
Possible Duplicate:
Where to find stdio.h functions implementations?
In C i have been using headers that contain prototypes and declarations of functions provided by the libraries, but where are functions like printf, scanf, etc. stored?
Where are they stored?
In which directory?
Why can't i find them? Are they stored as object files?
As everyone said, its int libc. You can search google for source code browser for the OS you are interested in, for linux I could find: http://lxr.linux.no/linux/
For netbsd, you can find printf and scanf here:
http://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libc/?only_with_tag=MAIN#dirlist
These functions are provided by the standard C library, often called libc.
In linux, you can find it under /lib/libc.so
In Windows they call it C Run-Time Libraries.
On Mac OS X, those functions are in stdio.h and is located in /usr/include. The library libc.dylib is in /usr/lib.
One place to check out is the section 3 of the manual. Then each individual function manual page lists the required header files and what additional libraries, if any, you need to link with.