Fix test: LLVMGetBitcodeModule takes ownership of memory buffer

[nhaehnle]

Summary

Clarify this behavior in the C interface header file and fix a related
bug in a test.

[foad]

llvm/include/llvm-c/BitReader.h

65

Spurious *

[nhaehnle]

llvm/include/llvm-c/BitReader.h

65

Thanks, fixing it.

[nhaehnle]

Address review comment

[nikic]

LGTM. Weird API.

llvm/include/llvm-c/BitReader.h

 /** Reads a module from the specified path, returning via the OutMP parameter
     a module provider which performs lazy deserialization. Returns 0 on success.
     Optionally returns a human-readable error message via OutMessage.
     This is deprecated. Use LLVMGetBitcodeModuleInContext2. */
 LLVMBool LLVMGetBitcodeModuleInContext(LLVMContextRef ContextRef,
                                        LLVMMemoryBufferRef MemBuf,
                                        LLVMModuleRef *OutM, char **OutMessage);
 
-/** Reads a module from the specified path, returning via the OutMP parameter a
- * module provider which performs lazy deserialization. Returns 0 on success. */
+/** Reads a module from the given memory buffer, returning via the OutMP
+ * parameter a  * module provider which performs lazy deserialization.
+ *
+ * Returns 0 on success.
+ *
+ * Takes ownership of \p MemBuf if (and only if) the module was read
+ * successfully. */
 LLVMBool LLVMGetBitcodeModuleInContext2(LLVMContextRef ContextRef,
                                         LLVMMemoryBufferRef MemBuf,
                                         LLVMModuleRef *OutM);
 
 /* This is deprecated. Use LLVMGetBitcodeModule2. */
 LLVMBool LLVMGetBitcodeModule(LLVMMemoryBufferRef MemBuf, LLVMModuleRef *OutM,
                               char **OutMessage);
 

llvm/tools/llvm-c-test/diagnostic.c

if (LLVMCreateMemoryBufferWithSTDIN(&MB, &msg)) {
     fprintf(stderr, "Error reading file: %s\n", msg);
     LLVMDisposeMessage(msg);
     return 1;
   }
 
 
   LLVMModuleRef M;
   int Ret = LLVMGetBitcodeModule2(MB, &M);
-  if (Ret) {
-    // We do not return if the bitcode was invalid, as we want to test whether
-    // the diagnostic handler was executed.
-    fprintf(stderr, "Error parsing bitcode: %s\n", msg);
-  }
-
+  if (Ret)
     LLVMDisposeMemoryBuffer(MB);
 
   if (handlerCalled) {
     fprintf(stderr, "Diagnostic handler was called while loading module\n");
   } else {
     fprintf(stderr, "Diagnostic handler was not called while loading module\n");
   }
 
   return 0;
 }