header file question

ntubski · 07-17-2012, 09:59 AM

Quote:

Originally Posted by mreff555

I'm speaking theoretically here, I'm not saying that there are more headers I should be adding or that the opencv library is poorly written. I'm simply trying to relate. Is the symptoms I'm describing something that could be seen when insufficient header information is included?

The symptoms you describe suggest memory corruption, try running with valgrind. I think -Wimplicit-int, -Wimplicit-function-declaration (both enabled by -Wall) would catch any missing header problems.

NevemTeve · 07-18-2012, 02:02 AM

Note: If a module doesn't include its own header, inconsistencies may arise. Use option -Wmissing-prototypes to detect this problem.

piyush.sharma · 07-18-2012, 04:22 AM

There are two kind of libraries that can link with our program
1. Static libraries (libdemo.a)
2. Dynamic libraries (libdemo.so) also known as shared objects

static libraries are merged when we binary is generated, but in case of shared objects they are linked to the binary.
I mention little more on this link
http://way2piyush.blogspot.in/2012/0...d-objects.html

shared objects can also be loaded and unloaded at run time via dlsym().

doughyi8u · 07-18-2012, 05:09 PM

How would I compile a simple "hello world" program using a static library (file.a) and not the standard libc.so?

NevemTeve · 07-18-2012, 11:13 PM

1. specify file.a at linkage: gcc -o hello hello.c file.a
2. not possible: libc is essential for every C program

piyush.sharma · 07-19-2012, 12:22 AM

create data.c
#include <stdio.h>
void hello()
{
printf("Hello !!! successful eith static library\n");
}

$gcc -Wall -c data.c
$ar -cvq libtest_static.a data.o

create abc.c
#include <stdio.h>
int main()
{
hello();
return 0;
}
$gcc -o abc abc.c libtest_static.a
$./abc

Note : all the file are stored in my current directory.
Hope it will help you.

pan64 · 07-19-2012, 12:34 AM

actually you can direct the linker to use static or dynamic libs: see the -static and -shared options. It depends on what libs are available (some libs have only static versions, some libs have only dynamic versions and some have both).