Add a new DynamicLoader plugin that uses SPI that are in development

for the fall (northern hemisphere) 2016 Darwin platforms to learn
about loaded images, instead of reading dyld internal data structures.
These new SPI don't exist on older releases, and new packets are
needed from debugserver to use them (those changes are already committed).

I had to change the minimum deployment target for debugserver in the xcode
project file to macOS 10.10 so that debugserver will use the 
[[NSProcessInfo processInfo] operatingSystemVersion]
call in MachProcess::GetOSVersionNumbers to get the operarting system
version # -- this API is only available in macOS 10.10 and newer
("OS X Yosemite", released Oct 2014).  If we have many people building
llvm.org lldb on older systems still, we can back off on this for the
llvm.org sources.

There should be no change in behavior with this commit, either to
older darwin systems or newer darwin systems.

For now the new DynamicLoader plugin is never activated - I'm forcing
the old plugin to be used in DynamicLoaderDarwin::UseDYLDSPI.
I'll remove that unconditional use of the old plugin soon, so the
newer plugin is used on the newest Darwin platforms.

<rdar://problem/25251243> 

llvm-svn: 276254

1 files changed, 11 insertions, 0 deletions

diff --git a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.h b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.h
index 637bd8640d2..81e16d1f454 100644
--- a/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.h
+++ b/lldb/source/Plugins/DynamicLoader/MacOSX-DYLD/DynamicLoaderMacOSXDYLD.h
@@ -7,6 +7,17 @@
 //
 //===----------------------------------------------------------------------===//
 
+
+// This is the DynamicLoader plugin for Darwin (macOS / iPhoneOS / tvOS / watchOS)
+// platforms earlier than 2016, where lldb would read the "dyld_all_image_infos"
+// dyld internal structure to understand where things were loaded and the 
+// solib loaded/unloaded notification function we put a breakpoint on gives us
+// an array of (load address, mod time, file path) tuples.
+//
+// As of late 2016, the new DynamicLoaderMacOS plugin should be used, which uses
+// dyld SPI functions to get the same information without reading internal dyld
+// data structures.
+
 #ifndef liblldb_DynamicLoaderMacOSXDYLD_h_
 #define liblldb_DynamicLoaderMacOSXDYLD_h_