| #include "library_file.h" | |
| #include <link.h> | |
| #include <stdio.h> | |
| // 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; | |
| } |