dlsym

问题 host.cpp has: int main (void) { void * th = dlopen("./p1.so", RTLD_LAZY); void * fu = dlsym(th, "fu"); ((void(*)(int, const char*)) fu)(2, "rofl"); return 0; } And p1.cpp has: #include <iostream> extern "C" bool fu (float * lol) { std::cout << "fuuuuuuuu!!!\n"; return true; } (I intentionally left errors checks out) When executing host, “fuuuuuuuu!!!” is printed correctly, even though I typecasted the void pointer to the symbol with a completely different function signature. Why did this

问题 I have a shared library which I want to access symbols from the main program. For example: main.c #include <stdio.h> void bar(void) { puts("bar"); } extern void foo(void); int main(void) { foo(); return 0; } foo.c #include <stdio.h> extern void bar(void); void foo(void) { puts("foo"); bar(); } I compile and run like: gcc -c -fpic foo.c gcc -shared -o libfoo.so foo.o gcc -L$(pwd) -o test main.c -lfoo ./test And I get the output I expect: foo bar However, I must use dlopen() and dlsym() because

问题 I have a shared library which I want to access symbols from the main program. For example: main.c #include <stdio.h> void bar(void) { puts("bar"); } extern void foo(void); int main(void) { foo(); return 0; } foo.c #include <stdio.h> extern void bar(void); void foo(void) { puts("foo"); bar(); } I compile and run like: gcc -c -fpic foo.c gcc -shared -o libfoo.so foo.o gcc -L$(pwd) -o test main.c -lfoo ./test And I get the output I expect: foo bar However, I must use dlopen() and dlsym() because

问题 Say I have a abstract base class defined like so: interface.hpp #ifndef INTERFACE_HPP #define INTERFACE_HPP 1 class interface{ public: virtual void func() = 0; }; #endif // INTERFACE_HPP Then I compile a translation unit test.cpp into a shared object test.so : test.cpp #include "interface.hpp" #include <iostream> class test_interface: public interface{ public: void func(){std::cout << "test_interface::func() called\n";} }; extern "C" interface &get_interface(){ static test_interface test;

问题 I get the following error when I try to run a script I have only execution access for: uname: symbol lookup error: /home/dumindara/random/sotest/a.out: undefined symbol: dlsym This is after I have set LD_PRELOAD environment variable to /home/dumindara/random/sotest/a.out . a.out has a test malloc function, and calls dlsym internally. I don't get this problem when running ls . Most processes do give this error. Why does this happen and what can I do to make it work? 回答1: I assume that your a

问题 I'm trying to write a hook for stat / lstat / fstat but I can't seem to get the original version from dlsym . I'm using the following code to obtain the original pointers. orig_stat = dlsym(RTLD_NEXT, "stat"); orig_lstat = dlsym(RTLD_NEXT, "lstat"); orig_fstat = dlsym(RTLD_NEXT, "fstat"); However, all three variables are set to null and calling dlerror also returns null . I'm creating the shared object with: clang fakestat.c -shared -fPIC -ldl -o fakestat.so and using my library by running a

问题 Is it possible to load a named unexported symbol from a framework using dlsym ? The symbol I'm trying to import has a name by which it is referred to within the framework. It is a function I need to call. I'm trying to do it the usual dlopen + dlsym way, but when I try to load a symbol that isn't exported, dlsym returns a NULL pointer. 回答1: dlsym can only load functions that are listed in the symbol table. You can list the symbol table by running nm on the framework in question. You can

问题 I am unable to propagate exceptions through dlsym. I use dlsym to load a cythonized python file. I made a minimal working example below so you can try it yourself: I have a pyx file, c_fun.pyx, which I compile to a C file using Cython. Then I'm using dlsym to load in the so file in another program, say use_fun.c++. You can use ./compile.sh to compile the files. On executing ./test, the program crashes with a segmentation fault. #c_fun.pyx: cdef public double _myfunction(double x) except*: a=1

问题 I'm using dlsym() in C and I have a question whether the return value of dlsym() should be explicitly cast or if it is implicitly cast correctly. Here is the function: double (*(compile)(void))(double x, double y) { if (system("scan-build clang -fPIC -shared -g -Wall -Werror -pedantic " "-std=c11 -O0 -lm foo.c -o foo.so") != 0) { exit(EXIT_FAILURE); } void *handle; handle = dlopen("./foo.so", RTLD_LAZY); if (!handle) { printf("Failed to load foo.so: %s\n", dlerror()); exit(EXIT_FAILURE); }

问题 i have the problem in writing a C++ framework, that users should have less overhead than possible to use it. Users can publish their work to the frameworks by creating a shared library that contains a class, which is derived by a frameworks' BaseClass and implementing an extern "C" createInstance()-method in order to return an instance its' derived class. So the framework can access the user class by calling the createInstance-Method through the shared library with dlsym(). class BaseClass{}