Exception handling in GCC 3.0.1 on AIX platform

Exception handling in GCC 3.0.1 on AIX platform

[Dmitry Dolgopolov]

Hello,

   Sometime ago I wrote about problems encountered with exceptions
   handling in GCC 3.0.1 on AIX 4.3.2.0 platform. Specifically, when
   exception is generated in a dynamicaly loaded module and tried to
   be catched in the program that loads that module. Following are the
   sample programs:

---
// testmain.cpp
#include <iostream>
#include <dlfcn.h>

int main() {
  void* handle = dlopen("./libshared.a", RTLD_LAZY | RTLD_GLOBAL);
  if (!handle) {
    std::cerr << "main:: Error during dlopen()" << std::endl;
    return 0;
  }
  void* symbol = dlsym(handle, "some_function");
  if (symbol) try {
    ((void (*)())symbol)();
  } catch (const std::string&) {
    std::cerr << "main:: Exception catched" << std::endl;
  } else {
    std::cerr << "main:: Error during dlsym()" << std::endl;
  }
  dlclose(handle);
  return 0;
}
---
// sharedlibrary.cpp
#include <iostream>
#include <dlfcn.h>

extern "C"
void some_function() {
  std::cerr << "some_function:: trace point" << std::endl;
  void* handle = dlopen("./libdeep.a", RTLD_LAZY | RTLD_GLOBAL);
  if (!handle) {
    std::cerr << "some_function:: Error during dlopen()" << std::endl;
    return;
  }
  void* symbol = dlsym(handle, "deep_function");
  if (symbol) try {
    ((void (*)())symbol)();
  } catch (const std::string&) {
    std::cerr << "some_function:: Exception catched" << std::endl;
  } else {
    std::cerr << "some_function:: Error during dlsym()" << std::endl;
  }
  dlclose(handle);
}
---
// deeplibrary.cpp
#include <iostream>

extern "C"
void deep_function() {
  std::cerr << "deep_function:: trace point" << std::endl;
  throw std::string("exception");
}
---

   Following commands were used during build:

c++ -pthread -Wl,-brtl -Wl,-bh:8 -o testmain testmain.cpp
c++ -pthread -shared -Wl,-G -Wl,-bh:8 -o libshared.a sharedlibrary.cpp
c++ -pthread -shared -Wl,-G -Wl,-bh:8 -o libdeep.a deeplibrary.cpp

   Then

chmod a+x,o-r *.a
slibclean

   Results of execution are as follows:

# ./testmain
some_function:: trace point
deep_function:: trace point
IOT/Abort trap (core dumped)

-- 
Best regards,
 Dmitry Dolgopolov                  mailto:d.dolgopolov@websci.ru

Re: Exception handling in GCC 3.0.1 on AIX platform

[David Edelsohn]

	You sent the same bug report last week.  Please stop sending the
same information.

Thanks, David

Re: Exception handling in GCC 3.0.1 on AIX platform

[David Edelsohn]

	At the moment, shared objects using exceptions need to have their
mode set "chmod o-r" so that they are loaded into the process-private
segment.

	BTW, if you are going to bother using -G/-brtl, you might as well
just use the ".so" extension for the file type.

David

Exception handling in GCC 3.0.1 on AIX platform

[Dmitry Dolgopolov]

Hello,

   We encountered the problem with exceptions handling in GCC 3.0.1 on
   AIX 4.3.2.0 platform. Specifically, when exception is generated in
   a dynamicaly loaded module and tried to be catched in the program
   that loads that module. Following are the sample programs:

---
// testmain.cpp
#include <iostream>
#include <dlfcn.h>

int main() {
  void* handle = dlopen("./libshared.a", RTLD_LAZY | RTLD_GLOBAL);
  if (!handle) {
    std::cerr << "main:: Error during dlopen()" << std::endl;
    return 0;
  }
  void* symbol = dlsym(handle, "some_function");
  if (symbol) try {
    ((void (*)())symbol)();
  } catch (const std::string&) {
    std::cerr << "main:: Exception catched" << std::endl;
  } else {
    std::cerr << "main:: Error during dlsym()" << std::endl;
  }
  dlclose(handle);
  return 0;
}
---
// sharedlibrary.cpp
#include <iostream>
#include <dlfcn.h>

extern "C"
void some_function() {
  std::cerr << "some_function:: trace point" << std::endl;
  void* handle = dlopen("./libdeep.a", RTLD_LAZY | RTLD_GLOBAL);
  if (!handle) {
    std::cerr << "some_function:: Error during dlopen()" << std::endl;
    return;
  }
  void* symbol = dlsym(handle, "deep_function");
  if (symbol) try {
    ((void (*)())symbol)();
  } catch (const std::string&) {
    std::cerr << "some_function:: Exception catched" << std::endl;
  } else {
    std::cerr << "some_function:: Error during dlsym()" << std::endl;
  }
  dlclose(handle);
}
---
// deeplibrary.cpp
#include <iostream>

extern "C"
void deep_function() {
  std::cerr << "deep_function:: trace point" << std::endl;
  throw std::string("exception");
}
---

   Following commands were used during build:

c++ -pthread -Wl,-brtl -Wl,-bh:8 -o testmain testmain.cpp
c++ -pthread -shared -Wl,-G -Wl,-bh:8 -o libshared.a sharedlibrary.cpp
c++ -pthread -shared -Wl,-G -Wl,-bh:8 -o libdeep.a deeplibrary.cpp

   Results of execution are as follows:

# ./testmain
some_function:: trace point
deep_function:: trace point
IOT/Abort trap (core dumped)

-- 
Best regards,
 Dmitry Dolgopolov                  mailto:d.dolgopolov@websci.ru