shared-libraries

I'm currently trying to port a C application to AIX and am getting confused. What are .a and .so files and how are they used when building/running an application? Archive libraries (.a) are statically linked i.e when you compile your program with -c option in gcc. So, if there's any change in library, you need to compile and build your code again. The advantage of .so (shared object) over .a library is that they are linked during the runtime i.e. after creation of your .o file -o option in gcc. So, if there's any change in .so file, you don't need to recompile your main program. But make sure

Why am I getting an "undefined reference" error using gcc? I am trying to create a shared object (.so) that exports one function, "external()". I then try to link against the .so but get "undefined reference 'external'". What am I doing wrong here? File: external.c int external() { return 5; } File: program.c int external(); int main(char** argv, int* argc) { return external(); } Commands: $ gcc -fPIC -c external.c $ gcc -shared -o libexternal.so external.o $ gcc -L. -lexternal -o program program.c /tmp/cc3MmhAE.o: In function `main': program.c:(.text+0x7): undefined reference to `external'

I'm trying to compile this source code from the makefile in a VPS, but its not working. The VPS is a 64 Cent OS Here's the full error # make gcc -c -O3 -w -DLINUX -I../SDK/amx/ ../SDK/amx/*.c g++ -c -O3 -w -DLINUX -I../SDK/amx/ ../SDK/*.cpp g++ -c -O3 -w -DLINUX -I../SDK/amx/ *.cpp g++ -O2 -fshort-wchar -shared -o "TCP_V1.so" *.o /usr/bin/ld: TCP-LINUX_V1.o: relocation R_X86_64_32 against `.rodata.str1.8' can not be used when making a shared object; recompile with -fPIC TCP-LINUX_V1.o: could not read symbols: Bad value collect2: ld returned 1 exit status make: *** [all] Error 1 Here's my

Is there a way to check which libraries is a running process using? To be more specific, if a program loads some shared libraries using dlopen , then readelf or ldd is not going to show it. Is it possible at all to get that information from a running process? If yes, how? Other people are on the right track. Here are a couple ways. cat /proc/NNNN/maps | awk '{print $6}' | grep '\.so' | sort | uniq Or, with strace: strace CMD.... 2>&1 | grep '^open(".*\.so"' Both of these assume that shared libraries have ".so" somewhere in their paths, but you can modify that. The first one gives fairly pretty

I have a shared library that is linked with another (third-party) shared library. My shared library is then loaded using dlopen in my application. All this works fine (assuming files are in the proper path etc). Now, the problem is that I don't even need to specify to link against the third-party shared library when I link my library. GCC accept it without reporting errors about undefined references. So, the question; how can I force GCC to notify me about undefined references ? If I change my library to be (temporarily) an executable, I get undefined references (when not supplying the library

So everyone probably knows that glibc's /lib/libc.so.6 can be executed in the shell like a normal executable in which cases it prints its version information and exits. This is done via defining an entry point in the .so. For some cases it could be interesting to use this for other projects too. Unfortunately, the low-level entry point you can set by ld's -e option is a bit too low-level: the dynamic loader is not available so you cannot call any proper library functions. glibc for this reason implements the write() system call via a naked system call in this entry point. My question now is,