[LibFuzzer] Reimplement how the optional user functions are called.
The motivation for this change is to fix linking issues on OSX.
However this only partially fixes linking issues (the uninstrumented
tests and a few others won't succesfully link yet).
This change introduces a struct of function pointers
(``fuzzer::ExternalFuntions``) which when initialised will point to the
optional functions if they are available. Currently these
``LLVMFuzzerInitialize`` and ``LLVMFuzzerCustomMutator`` functions.
Two implementations of ``fuzzer::ExternalFunctions`` constructor are
provided one for Linux and one for OSX.
The OSX implementation uses ``dlsym()`` because the prior implementation
using weak symbols does not work unless the additional flags are passed
to the linker.
The Linux implementation continues to use weak symbols because the
``dlsym()`` approach does not work unless additional flags are passed
to the linker.
Differential Revision: http://reviews.llvm.org/D20741
llvm-svn: 271491
diff --git a/llvm/lib/Fuzzer/FuzzerExtFunctions.h b/llvm/lib/Fuzzer/FuzzerExtFunctions.h
new file mode 100644
index 0000000..95b5240
--- /dev/null
+++ b/llvm/lib/Fuzzer/FuzzerExtFunctions.h
@@ -0,0 +1,32 @@
+//===- FuzzerExtFunctions.h - Interface to external functions ---*- C++ -* ===//
+//
+// The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// Defines an interface to (possibly optional) functions.
+//===----------------------------------------------------------------------===//
+#ifndef LLVM_FUZZER_EXT_FUNCTIONS_H
+#define LLVM_FUZZER_EXT_FUNCTIONS_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+namespace fuzzer {
+
+struct ExternalFunctions {
+ // Initialize function pointers. Functions that are not available
+ // will be set to nullptr.
+ ExternalFunctions();
+
+#define EXT_FUNC(NAME, RETURN_TYPE, FUNC_SIG, WARN) \
+ RETURN_TYPE(*NAME) FUNC_SIG = nullptr
+
+#include "FuzzerExtFunctions.def"
+
+#undef EXT_FUNC
+};
+} // namespace fuzzer
+#endif