[Support] Add a basic C API for llvm::Error.

Summary:
The C-API supports consuming errors, converting an error to a string error
message, and querying an error's type. Other LLVM C APIs that wish to use
llvm::Error can supply error-type-id checkers and custom
error-to-structured-type converters for any custom errors they provide.

Reviewers: bogner, zturner, labath, dblaikie

Subscribers: llvm-commits

Differential Revision: https://reviews.llvm.org/D50716

llvm-svn: 339802

1 files changed, 65 insertions, 0 deletions

diff --git a/llvm/include/llvm-c/Error.h b/llvm/include/llvm-c/Error.h
new file mode 100644
index 00000000000..00714ec950e
--- /dev/null
+++ b/llvm/include/llvm-c/Error.h
@@ -0,0 +1,65 @@
+/*===------- llvm-c/Error.h - llvm::Error class C Interface -------*- C -*-===*\
+|*                                                                            *|
+|*                     The LLVM Compiler Infrastructure                       *|
+|*                                                                            *|
+|* This file is distributed under the University of Illinois Open Source      *|
+|* License. See LICENSE.TXT for details.                                      *|
+|*                                                                            *|
+|*===----------------------------------------------------------------------===*|
+|*                                                                            *|
+|* This file defines the C interface to LLVM's Error class.                   *|
+|*                                                                            *|
+\*===----------------------------------------------------------------------===*/
+
+#ifndef LLVM_C_ERROR_H
+#define LLVM_C_ERROR_H
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * Opaque reference to an error instance. Null serves as the 'success' value.
+ */
+typedef struct LLVMOpaqueError *LLVMErrorRef;
+
+/**
+ * Error type identifier.
+ */
+typedef const void *LLVMErrorTypeId;
+
+/**
+ * Returns the type id for the given error instance, which must be a failure
+ * value (i.e. non-null).
+ */
+LLVMErrorTypeId LLVMGetErrorTypeId(LLVMErrorRef Err);
+
+/**
+ * Dispose of the given error without handling it. This operation consumes the
+ * error, and the given LLVMErrorRef value is not usable once this call returns.
+ * Note: This method *only* needs to be called if the error is not being passed
+ * to some other consuming operation, e.g. LLVMGetErrorMessage.
+ */
+void LLVMConsumeError(LLVMErrorRef Err);
+
+/**
+ * Returns the given string's error message. This operation consumes the error,
+ * and the given LLVMErrorRef value is not usable once this call returns.
+ */
+char *LLVMGetErrorMessage(LLVMErrorRef Err);
+
+/**
+ * Dispose of the given error message.
+ */
+void LLVMDisposeErrorMessage(char *ErrMsg);
+
+/**
+ * Returns the type id for llvm StringError.
+ */
+LLVMErrorTypeId LLVMGetStringErrorTypeId();
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif