Initial checking of C++ exception handling library

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@8146 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 223 insertions, 0 deletions

diff --git a/runtime/GCCLibraries/libexception/C++-Exception.cpp b/runtime/GCCLibraries/libexception/C++-Exception.cpp
new file mode 100644
index 0000000000..7ed78688ea
--- /dev/null
+++ b/runtime/GCCLibraries/libexception/C++-Exception.cpp
@@ -0,0 +1,223 @@
+//===- c++-exception.cpp - Exception handling support for C++ exceptions --===//
+//
+// This file defines the methods used to implement C++ exception handling in
+// terms of the invoke and %llvm.unwind intrinsic.  These primitives implement
+// an exception handling ABI similar (but simpler and more efficient than) the
+// Itanium C++ ABI exception handling standard.
+//
+//===----------------------------------------------------------------------===//
+
+#include "c++-exception.h"
+#include <cstdlib>
+#include <cassert>
+
+//===----------------------------------------------------------------------===//
+// Generic exception support
+//
+
+// Thread local state for exception handling.
+// FIXME: This should really be made thread-local!
+//
+static llvm_exception *CaughtExceptionStack = 0;
+
+// UncaughtExceptionStack - The stack of exceptions currently being thrown.
+static llvm_exception *UncaughtExceptionStack = 0;
+
+// __llvm_eh_has_uncaught_exception - This is used to implement
+// std::uncaught_exception.
+//
+bool __llvm_eh_has_uncaught_exception(void) {
+  return UncaughtExceptionStack != 0;
+}
+
+// __llvm_eh_current_uncaught_exception - This function checks to see if the
+// current uncaught exception is of the specified language type.  If so, it
+// returns a pointer to the exception area data.
+//
+void *__llvm_eh_current_uncaught_exception_type(unsigned HandlerType) {
+  assert(UncaughtExceptionStack && "No uncaught exception!");
+  if (UncaughtExceptionStack->ExceptionType == HandlerType)
+    return UncaughtExceptionStack+1;
+  return 0;
+}
+
+
+/*===----------------------------------------------------------------------===**
+ * C++ Specific exception handling support...
+ */
+
+// __llvm_cxxeh_allocate_exception - This function allocates space for the
+// specified number of bytes, plus a C++ exception object header.
+//
+void *__llvm_cxxeh_allocate_exception(unsigned NumBytes) {
+  // FIXME: This should eventually have back-up buffers for out-of-memory
+  // situations.
+  //
+  llvm_cxx_exception *E =
+    (llvm_cxx_exception *)malloc(NumBytes+sizeof(llvm_cxx_exception));
+  E->BaseException.ExceptionType = 0; // intialize to invalid
+
+  return E+1;   // return the pointer after the header
+}
+
+// __llvm_cxxeh_free_exception - Low-level function to free an exception.  This
+// is called directly from generated C++ code if evaluating the exception value
+// into the exception location throws.  Otherwise it is called from the C++
+// exception object destructor.
+//
+void __llvm_cxxeh_free_exception(void *ObjectPtr) {
+  llvm_cxx_exception *E = (llvm_cxx_exception *)ObjectPtr - 1;
+  free(E);
+}
+
+// cxx_destructor - This function is called through the generic
+// exception->ExceptionDestructor function pointer to destroy a caught
+// exception.
+//
+static void cxx_destructor(llvm_exception *LE) {
+  void *ObjectPtr = LE+1;
+  llvm_cxx_exception *E = (llvm_cxx_exception *)ObjectPtr - 1;
+
+  // The exception is no longer caught.
+  assert(CaughtExceptionStack == LE &&
+         "Destroying an exception which is not the current caught exception?");
+  CaughtExceptionStack = LE->Next;
+
+  struct ExceptionFreer {
+    void *Ptr;
+    ExceptionFreer(void *P) : Ptr(P) {}
+    ~ExceptionFreer() {
+      // Free the memory for the exception, when the function is left, even if
+      // the exception object dtor throws its own exception!
+      __llvm_cxxeh_free_exception(Ptr);
+    }
+  } EF(E+1);
+  
+  // Run the exception object dtor if it exists. */
+  if (E->ExceptionObjectDestructor)
+    E->ExceptionObjectDestructor(E);
+}
+
+// __llvm_cxxeh_throw - Given a pointer to memory which has an exception object
+// evaluated into it, this sets up all of the fields of the exception allowing
+// it to be thrown.  After calling this, the code should call %llvm.unwind
+//
+void __llvm_cxxeh_throw(void *ObjectPtr, const std::type_info *TypeInfoPtr,
+                        void (*DtorPtr)(void*)) {
+  llvm_cxx_exception *E = (llvm_cxx_exception *)ObjectPtr - 1;
+  E->BaseException.ExceptionDestructor = cxx_destructor;
+  E->BaseException.ExceptionType = CXXException;
+  E->BaseException.Next = UncaughtExceptionStack;
+  UncaughtExceptionStack = &E->BaseException;
+  E->BaseException.HandlerCount = 0;
+
+  E->TypeInfo = TypeInfoPtr;
+  E->ExceptionObjectDestructor = DtorPtr;
+  E->UnexpectedHandler = 0;  /* FIXME */
+  E->TerminateHandler = 0;   /* FIXME */
+}
+
+// __llvm_cxxeh_current_uncaught_exception_isa - This function checks to see if
+// the current uncaught exception is a C++ exception, and if it is of the
+// specified type id.  If so, it returns a pointer to the object adjusted as
+// appropriate, otherwise it returns null.
+//
+void *__llvm_cxxeh_current_uncaught_exception_isa(
+                                         const std::type_info *CatchType) {
+  assert(UncaughtExceptionStack && "No uncaught exception!");
+  if (UncaughtExceptionStack->ExceptionType != CXXException)
+    return 0;     /* If it's not a c++ exception, it doesn't match! */
+
+  // If it is a C++ exception, use the type info object stored in the exception
+  // to see if TypeID matches and, if so, to adjust the exception object
+  // pointer.
+  //
+  llvm_cxx_exception *E = (llvm_cxx_exception*)UncaughtExceptionStack;
+
+  // ThrownPtr is a pointer to the object being thrown...
+  void *ThrownPtr = E+1;
+  const std::type_info *ThrownType = E->TypeInfo;
+
+  // FIXME: this code exists in the GCC exception handling library: I haven't
+  // thought about this yet, so it should be verified at some point!
+#if 1
+  // Pointer types need to adjust the actual pointer, not
+  // the pointer to pointer that is the exception object.
+  // This also has the effect of passing pointer types
+  // "by value" through the __cxa_begin_catch return value.
+  if (ThrownType->__is_pointer_p())
+    ThrownPtr = *(void **)ThrownPtr;
+#endif
+
+  if (CatchType->__do_catch(ThrownType, &ThrownPtr, 1))
+    return ThrownPtr;
+
+  return 0;
+}
+
+
+/* __llvm_cxxeh_begin_catch - This function is called by "exception handlers",
+ * which transition an exception from being uncaught to being caught.  It
+ * returns a pointer to the exception object portion of the exception.  This
+ * function must work with foreign exceptions.
+ */
+void *__llvm_cxxeh_begin_catch(void) {
+  llvm_exception *E = UncaughtExceptionStack;
+  assert(UncaughtExceptionStack && "There are no uncaught exceptions!?!?");
+
+  /* The exception is now no longer uncaught... */
+  UncaughtExceptionStack = E->Next;
+  
+  /* The exception is now caught... */
+  E->Next = CaughtExceptionStack;
+  CaughtExceptionStack = E->Next;
+
+  /* Increment the handler count for this exception. */
+  E->HandlerCount++;
+
+  /* Return a pointer to the exception object */
+  return E+1;
+}
+
+/* __llvm_cxxeh_end_catch - This function decrements the HandlerCount of the
+ * top-level caught exception, destroying it if this is the last handler for the
+ * exception.
+ */
+void __llvm_cxxeh_end_catch(void) {
+  llvm_exception *E = CaughtExceptionStack;
+  assert(E && "There are no caught exceptions!");
+  
+  /* If this is the last handler using the exception, destroy it now! */
+  if (--E->HandlerCount == 0) {
+    CaughtExceptionStack = E->Next;   /* Unlink from the stack */
+    E->ExceptionDestructor(E);        /* Release memory for the exception */
+  }
+}
+
+/* __llvm_cxxeh_rethrow - This function turns the top-level caught exception
+ * into an uncaught exception, in preparation for an llvm.unwind, which should
+ * follow immediately after the call to this function.  This function must be
+ * prepared to deal with foreign exceptions.
+ */
+void __llvm_cxxeh_rethrow(void) {
+  llvm_exception *E = CaughtExceptionStack;
+  if (E == 0) {
+    /* 15.1.8 - If there are no uncaught exceptions being thrown, 'throw;'
+     * should call terminate.
+     */
+    /* FIXME */assert(0 && "FIXME: this should call E->Terminate!");
+  }
+
+  /* Otherwise we have an exception to rethrow. Move it back to the uncaught
+   * stack.
+   */
+  CaughtExceptionStack = E->Next;
+  E->Next = UncaughtExceptionStack;
+  UncaughtExceptionStack = E;
+
+  /* Decrement the number of handlers which are using the exception. */
+  --E->HandlerCount;
+  
+  /* Return to the caller, which should perform the unwind now. */
+}
+