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

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

llvm-svn: 179082

1 files changed, 8 insertions, 5 deletions

diff --git a/clang/docs/ThreadSanitizer.rst b/clang/docs/ThreadSanitizer.rst
index c0c576b44a5..5e5ee48f7f4 100644
--- a/clang/docs/ThreadSanitizer.rst
+++ b/clang/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
 --------------