#include "library_file.h" #include #include // Make a duplicate "_r_debug" symbol that is visible. This is the global // variable name that the dynamic loader uses to communicate changes in shared // libraries that get loaded and unloaded. LLDB finds the address of this // variable by reading the DT_DEBUG entry from the .dynamic section of the main // executable. // What will happen is the dynamic loader will use the "_r_debug" symbol from // itself until the a.out executable gets loaded. At this point the new // "_r_debug" symbol will take precedence over the orignal "_r_debug" symbol // from the dynamic loader and the copy below will get updated with shared // library state changes while the version that LLDB checks in the dynamic // loader stays the same for ever after this. // // When our DYLDRendezvous.cpp tries to check the state in the _r_debug // structure, it will continue to get the last eAdd as the state before the // switch in symbol resolution. // // Before a fix in LLDB, this would mean that we wouldn't ever load any shared // libraries since DYLDRendezvous was waiting to see a eAdd state followed by a // eConsistent state which would trigger the adding of shared libraries, but we // would never see this change because the local copy below is actually what // would get updated. Now if DYLDRendezvous detects two eAdd states in a row, // it will load the shared libraries instead of doing nothing and a log message // will be printed out if "log enable lldb dyld" is active. r_debug _r_debug; int main() { library_function(); // Break here return 0; }