[Switch] about Linux static library and dynamic library

Create static and dynamic libraries in Linux

Source code

----------- A. cpp ---------------
# Include <cstdio>
Int A (int I)
{
STD: printf ("in a (int A) % DN", I );
Return 0;
}

----------- B. cpp ----------------
# Include <iostream>
Int B (char * s)
{
STD: cout <"in int B (char * s):" <S <STD: Endl;
Return 0;
}
---------- Main. cpp --------------
# Include <cstdio>
Using namespace STD;
Int A (int I );
Int B (char * s );
Int main ()
{
A (5 );
B ("OK ");
Printf ("in mainn ");
Return 0;
}

Static Library
1. Compile a. o B. o file
# G ++-c a. cpp B. cpp

2. Generate the archive file libtest. a c-create R-Add the file to libtest.
# Ar RC libtest. a A. o B. O

3. Specify the static library libtest. A for compilation.
# G ++-O main. cpp libtest.

Running result
#./A. Out
In a (int A) 5
In int B (char * s): OK
In Main

For libtest.CodeCopying is equivalent to static compilation.

Dynamic library
1. compile and generate a. o B. o file-FPIC when generating the. o file, use the relative address to implement code location independence.
# G ++-fpic a. cpp B. cpp

2. Generate the dynamic library libtest. So
# G ++-shared-O libtest. So a. o B. o

3. Specify the dynamic library libtest. So for compilation.
# G ++ main. cpp./libtest. So

View the dynamic Connection Library
# ldd. out
. /libtest. so =>. /libtest. so (0x40014000)
libstdc ++-libc6.2-2. so.3 =>/usr/lib/libstdc ++-libc6.2-2. so.3 (0x4002e000)
libm. so.6 =>/lib/i686/libm. so.6 (0x40071000)
libc. so.6 =>/lib/i686/libc. so.6 (0x42000000)
/lib/ld-linux.so.2 =>/lib/ld-linux.so.2 (0x40000000)
/lib/ld-linux.so.2 =>/lib/ld-linux.so.2 (0x40000000)

Others
1. When dynamically connecting to database 3, if
# G ++ main. cpp libtest. So
The libtest. So library cannot be found in the default library path.
#./A. Out
./A. Out: Error while loading shared libraries: libtest. So: cannot open shared object file: no such
File or directory
View connected database
# Ldd a. Out
Libtest. So => not found
Libstdc ++-libc6.2-2. so.3 =>/usr/lib/libstdc ++-libc6.2-2. so.3 (0x4002c000)
Libm. so.6 =>/lib/i686/libm. so.6 (0x4006f000)
Libc. so.6 =>/lib/i686/libc. so.6 (0x42000000)
/Lib/ld-linux.so.2 =>/lib/ld-linux.so.2 (0x40000000)

2. For ease of use, you can copy the static library libtest. A or the dynamic library libtest. So to/lib or/usr/lib in the search path of the default library,
Compile directly
# G ++ main. cpp-ltest
-L automatic library name extension
# Ldd a. Out
Libtest. So =>/usr/lib/libtest. So (0x4002b000)
Libstdc ++-libc6.2-2. so.3 =>/usr/lib/libstdc ++-libc6.2-2. so.3 (0x4002e000)
Libm. so.6 =>/lib/i686/libm. so.6 (0x40071000)
Libc. so.6 =>/lib/i686/libc. so.6 (0x42000000)
/Lib/ld-linux.so.2 =>/lib/ld-linux.so.2 (0x40000000)
Static condition
# G ++ main. cpp-ltest
# Ldd a. Out
Libstdc ++-libc6.2-2. so.3 =>/usr/lib/libstdc ++-libc6.2-2. so.3 (0x4002b000)
Libm. so.6 =>/lib/i686/libm. so.6 (0x4006f000)
Libc. so.6 =>/lib/i686/libc. so.6 (0x42000000)
/Lib/ld-linux.so.2 =>/lib/ld-linux.so.2 (0x40000000)

3. After archive is generated in static library 2, ranlib libtest. A may need to write the content index to libtest. A for LD connection.

4. The-L option should be placed behind the compiled file. An error will occur before it.
# G ++-ltest main. cpp
/Tmp/ccbqk3ky. O: In function 'main ':
/Tmp/ccbqk3ky. O (. Text + 0xc): Undefined reference to 'a (INT )'
/Tmp/ccbqk3ky. O (. Text + 0x1c): Undefined reference to 'B (char *)'
Collect2: LD returned 1 exit status

 

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