.so experiment

.so means shared lib.

We call it Dynamic Linking, against Static.

f1.c --->libF1LIB.so

main.c---->libmai.so

Link libmai.so +libF1LIB.so  ---> a.out

The very basic facts is:

1. a.out  which is the executive, has no storage for f1.so.   

When a.out is executed,  it will find where f1.so is and loaded at the very executing time.

2. Size:

libF1LIB.so  --->7,856 BYTES

libmai.so  --> 8144 BYTES

a.out --> 8632 BYTES

We find that 8632 != 8144+7856

It is almost the same size as its libmai.so

3. Move a.out to another directory and still executed OK.

----which means IT remember where it is born and first link address (original libF1LIB.so) and can find that.

4. Delete libF1LIB.so then execute a.out.  IT Doesn't work.

--error: can not find libF1LIB.so

5. IF we reserve a libF1LIB.so in directory /lib or /usr/lib  then execute a.out.    IT works.

--we find It will search first in original directory, and then search the environmental variable PATH's directory.

--It searches the name or the string you input in your CMakeLists.txt or Makefile. Here the name is "libF1LIB.so".

--If "libF1LIB.so" is found, the fill the table of address of "unresolved external symbol" of both Variable and Function.