There were numerous issues here that were all entangled, and so I've
tried to do a general simplification of the logic.
1) The logic was mimicing actual GCC bugs, rather than "features". These
have been fixed in trunk GCC, and this fixes Clang as well. Notably,
the logic was always intended to be last-match-wins like any other
flag.
2) The logic for handling '-mdynamic-no-pic' was preposterously unclear.
It also allowed the use of this flag on non-Darwin platforms where it
has no actual meaning. Now this option is handled directly based on
tests of how llvm-gcc behaves, and it is only supported on Darwin.
3) The APIs for the Driver's ToolChains had the implementation ugliness
of dynamic-no-pic leaking through them. They also had the
implementation details of the LLVM relocation model flag names
leaking through.
4) The actual results of passing these flags was incorrect on Darwin in
many cases. For example, Darwin *always* uses PIC level 2 if it uses
in PIC level, and Darwin *always* uses PIC on 64-bit regardless of
the flags specified, including -fPIE. Darwin never compiles in PIE
mode, but it can *link* in PIE mode.
5) Also, PIC was not always being enabled even when PIE was. This isn't
a supported mode at all and may have caused some fallout in builds
with complex PIC and PIE interactions.
The result is (I hope) cleaner and clearer for readers. I've also left
comments and tests about some of the truly strage behavior that is
observed on Darwin platforms. We have no real testing of Windows
platforms and PIC, but I don't have the tools handy to figure that out.
Hopefully others can beef up our testing here.
Unfortunately, I can't test this for every platform. =/ If folks have
dependencies on these flags that aren't covered by tests, they may
break. I've audited and ensured that all the changes in behavior of the
existing tests are intentional and good. In particular I've tried to
make sure the Darwin behavior (which is more suprising than the Linux
behavior) also matches that of 'gcc' on my mac.
llvm-svn: 168297
- Separately check if -fPIE was specified in the command line and define both __PIC__ and __PIE__ when -fPIE is used. We need to check this separately because -fPIE will infer -fPIC even if its not explicitly used.
- Fixed existing tests.
- Added new tests for cases where both -fPIC and -fPIE is used.
Author: Tareq A. Siraj <tareq.a.siraj@intel.com>
Fixes: PR13221
Review: http://llvm-reviews.chandlerc.com/D94
llvm-svn: 167846
First, this patch cleans up the parsing of the PIC and PIE family of
options in the driver. The existing logic failed to claim arguments all
over the place resulting in kludges that marked the options as unused.
Instead actually walk all of the arguments and claim them properly.
We now treat -f{,no-}{pic,PIC,pie,PIE} as a single set, accepting the
last one on the commandline. Previously there were lots of ordering bugs
that could creep in due to the nature of the parsing. Let me know if
folks would like weird things such as "-fPIE -fno-pic" to turn on PIE,
but disable full PIC. This doesn't make any sense to me, but we could in
theory support it.
Options that seem to have intentional "trump" status (-static, -mkernel,
etc) continue to do so and are commented as such.
Next, a -pie-level flag is threaded into the frontend, rigged to
a language option, and handled preprocessor, setting up the appropriate
defines. We'll now have the correct defines when compiling with -fpie.
The one place outside of the preprocessor that was inspecting the PIC
level (as opposed to the relocation model, which is set and handled
separately, yay!) is in the GNU ObjC runtime. I changed it to exactly
preserve existing behavior. If folks want to change its behavior in the
face of PIE, they can do that in a separate patch.
Essentially the only functionality changed here is the preprocessor
defines and bug-fixes to the argument management.
Tests have been updated and extended to test all of this a bit more
thoroughly.
llvm-svn: 154291
Alp Toker