PengZheng commented on PR #441:
URL: https://github.com/apache/celix/pull/441#issuecomment-1239468298
> The challenge I see here is the same as with importing/exporting libraries
from bundles: If there are libraries which are different, but have the same
SONAME header, a call to dlopen will reuse a (transitive) library with the same
SONAME instead of loading a new lib. This is even true if DL_LOCAL is used.
It turns out that if we provide the full absolute path to `dlopen`, we may
workaround the problem. I check the following example on my Linux machine:
```CMake
# CMakeLists.txt
cmake_minimum_required(VERSION 3.23)
project(hello_solib C)
set(CMAKE_C_STANDARD 99)
add_library(hello_impl1 SHARED hello1.c)
set_target_properties(hello_impl1 PROPERTIES LIBRARY_OUTPUT_DIRECTORY
${CMAKE_CURRENT_BINARY_DIR}/impl1)
set_target_properties(hello_impl1 PROPERTIES OUTPUT_NAME hello)
add_library(hello_impl2 SHARED hello2.c)
set_target_properties(hello_impl2 PROPERTIES LIBRARY_OUTPUT_DIRECTORY
${CMAKE_CURRENT_BINARY_DIR}/impl2)
set_target_properties(hello_impl2 PROPERTIES OUTPUT_NAME hello)
add_executable(hello_solib main.c)
target_compile_definitions(hello_solib PRIVATE
HELLO1_LOC="$<TARGET_FILE:hello_impl1>")
target_compile_definitions(hello_solib PRIVATE
HELLO2_LOC="$<TARGET_FILE:hello_impl2>")
target_link_libraries(hello_solib PRIVATE dl)
```
```C
//main.c
#include "hello.h"
#include <assert.h>
#include <dlfcn.h>
#include <stdio.h>
int main() {
int (*funcp1)(void);
int (*funcp2)(void);
void *handle1;
void *handle2;
printf("impl1=%s\n", HELLO1_LOC);
handle1 = dlopen(HELLO1_LOC, RTLD_LAZY);
assert(handle1 != NULL);
printf("impl2=%s\n", HELLO2_LOC);
handle2 = dlopen(HELLO2_LOC, RTLD_LAZY);
assert(handle2 != NULL);
*(void **)(&funcp2) = dlsym(handle2, "hello");
funcp2();
*(void **)(&funcp1) = dlsym(handle1, "hello");
funcp1();
dlclose(handle2);
dlclose(handle1);
return 0;
}
```
```C
//hello.h
#ifndef HELLO_SOLIB_HELLO_H
#define HELLO_SOLIB_HELLO_H
#ifdef __cplusplus
extern "C" {
#endif
int hello(void);
#ifdef __cplusplus
}
#endif
#endif //HELLO_SOLIB_HELLO_H
```
```C
//hello1.c
#include "hello.h"
#include <stdio.h>
int hello(void) {
printf("hello1\n");
}
```
```C
//hello2.c
#include "hello.h"
#include <stdio.h>
int hello(void) {
printf("hello2\n");
}
```
Running the binary produces the following console output:
```
/home/peng/Downloads/hello_solib/cmake-build-debug/hello_solib
impl1=/home/peng/Downloads/hello_solib/cmake-build-debug/impl1/libhello.so
impl2=/home/peng/Downloads/hello_solib/cmake-build-debug/impl2/libhello.so
hello2
hello1
Process finished with exit code 0
```
I don't use Mac, and thus can not check for MacOS.
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