If the user requested a zero-base-shadow sanitizer, infer -pie and -fPIC when appropriate.

Differential Revision: http://llvm-reviews.chandlerc.com/D502

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179082 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 14 insertions, 8 deletions

diff --git a/docs/MemorySanitizer.rst b/docs/MemorySanitizer.rst
index fdb8a81023..439acc47fa 100644
--- a/docs/MemorySanitizer.rst
+++ b/docs/MemorySanitizer.rst
@@ -46,7 +46,7 @@ to disable inlining (just use ``-O1``) and tail call elimination
       return 0;
     }
 
-    % clang -fsanitize=memory -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cc
+    % clang -fsanitize=memory -fno-omit-frame-pointer -g -O2 umr.cc
 
 If a bug is detected, the program will print an error message to
 stderr and exit with a non-zero exit code. Currently, MemorySanitizer
@@ -103,7 +103,7 @@ the example above,
 
 .. code-block:: console
 
-    % clang -fsanitize=memory -fsanitize-memory-track-origins -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cc
+    % clang -fsanitize=memory -fsanitize-memory-track-origins -fno-omit-frame-pointer -g -O2 umr.cc
     % ./a.out 2>log
     % projects/compiler-rt/lib/asan/scripts/asan_symbolize.py / < log | c++filt
     ==14425==  WARNING: MemorySanitizer: UMR (uninitialized-memory-read)
@@ -160,7 +160,10 @@ Limitations
   address space. This means that tools like ``ulimit`` may not work as
   usually expected.
 * Static linking is not supported.
-* Non-position-independent executables are not supported.
+* Non-position-independent executables are not supported.  Therefore, the
+  ``fsanitize=memory`` flag will cause Clang to act as though the ``-fPIE``
+  flag had been supplied if compiling without ``-fPIC``, and as though the
+  ``-pie`` flag had been supplied if linking an executable.
 * Depending on the version of Linux kernel, running without ASLR may
   be not supported. Note that GDB disables ASLR by default. To debug
   instrumented programs, use "set disable-randomization off".
diff --git a/docs/ThreadSanitizer.rst b/docs/ThreadSanitizer.rst
index c0c576b44a..5e5ee48f7f 100644
--- a/docs/ThreadSanitizer.rst
+++ b/docs/ThreadSanitizer.rst
@@ -25,9 +25,9 @@ platforms is problematic and not yet planned.
 Usage
 -----
 
-Simply compile your program with ``-fsanitize=thread -fPIE`` and link it with
-``-fsanitize=thread -pie``.  To get a reasonable performance add ``-O1`` or
-higher.  Use ``-g`` to get file names and line numbers in the warning messages.
+Simply compile and link your program with ``-fsanitize=thread``.  To get a
+reasonable performance add ``-O1`` or higher.  Use ``-g`` to get file names
+and line numbers in the warning messages.
 
 Example:
 
@@ -48,7 +48,7 @@ Example:
     return Global;
   }
 
-  $ clang -fsanitize=thread -g -O1 tiny_race.c -fPIE -pie
+  $ clang -fsanitize=thread -g -O1 tiny_race.c
 
 If a bug is detected, the program will print an error message to stderr.
 Currently, ThreadSanitizer symbolizes its output using an external
@@ -107,7 +107,10 @@ Limitations
 * ThreadSanitizer maps (but does not reserve) a lot of virtual address space.
   This means that tools like ``ulimit`` may not work as usually expected.
 * Libc/libstdc++ static linking is not supported.
-* ThreadSanitizer requires ``-fPIE -pie`` compiler flags.
+* Non-position-independent executables are not supported.  Therefore, the
+  ``fsanitize=thread`` flag will cause Clang to act as though the ``-fPIE``
+  flag had been supplied if compiling without ``-fPIC``, and as though the
+  ``-pie`` flag had been supplied if linking an executable.
 
 Current Status
 --------------