Prevent diagnostic memory leak (#2110)

Fixes https://crbug.com/906669

* Don't free diagnostics in spvBinaryParse
* When invoking the parser we wish to ignore the error messages from,
instead create a hijacked context and replace the message consumer with
a null consumer

include/spirv-tools/libspirv.h

@@ -565,8 +565,8 @@ SPIRV_TOOLS_EXPORT void spvReducerOptionsSetSeed(spv_reducer_options options,
 // Encodes the given SPIR-V assembly text to its binary representation. The
 // length parameter specifies the number of bytes for text. Encoded binary will
 // be stored into *binary. Any error will be written into *diagnostic if
-// diagnostic is non-null. The generated binary is independent of the context
-// and may outlive it.
+// diagnostic is non-null, otherwise the context's message consumer will be
+// used. The generated binary is independent of the context and may outlive it.
 SPIRV_TOOLS_EXPORT spv_result_t spvTextToBinary(const spv_const_context context,
                                                 const char* text,
                                                 const size_t length,
@@ -588,7 +588,8 @@ SPIRV_TOOLS_EXPORT void spvTextDestroy(spv_text text);
 // word_count parameter specifies the number of words for binary. The options
 // parameter is a bit field of spv_binary_to_text_options_t. Decoded text will
 // be stored into *text. Any error will be written into *diagnostic if
-// diagnostic is non-null.
+// diagnostic is non-null, otherwise the context's message consumer will be
+// used.
 SPIRV_TOOLS_EXPORT spv_result_t spvBinaryToText(const spv_const_context context,
                                                 const uint32_t* binary,
                                                 const size_t word_count,
@@ -601,20 +602,22 @@ SPIRV_TOOLS_EXPORT spv_result_t spvBinaryToText(const spv_const_context context,
 SPIRV_TOOLS_EXPORT void spvBinaryDestroy(spv_binary binary);
 
 // Validates a SPIR-V binary for correctness. Any errors will be written into
-// *diagnostic if diagnostic is non-null.
+// *diagnostic if diagnostic is non-null, otherwise the context's message
+// consumer will be used.
 SPIRV_TOOLS_EXPORT spv_result_t spvValidate(const spv_const_context context,
                                             const spv_const_binary binary,
                                             spv_diagnostic* diagnostic);
 
 // Validates a SPIR-V binary for correctness. Uses the provided Validator
 // options. Any errors will be written into *diagnostic if diagnostic is
-// non-null.
+// non-null, otherwise the context's message consumer will be used.
 SPIRV_TOOLS_EXPORT spv_result_t spvValidateWithOptions(
     const spv_const_context context, const spv_const_validator_options options,
     const spv_const_binary binary, spv_diagnostic* diagnostic);
 
 // Validates a raw SPIR-V binary for correctness. Any errors will be written
-// into *diagnostic if diagnostic is non-null.
+// into *diagnostic if diagnostic is non-null, otherwise the context's message
+// consumer will be used.
 SPIRV_TOOLS_EXPORT spv_result_t
 spvValidateBinary(const spv_const_context context, const uint32_t* words,
                   const size_t num_words, spv_diagnostic* diagnostic);
@@ -661,7 +664,8 @@ typedef spv_result_t (*spv_parsed_instruction_fn_t)(
 // is supplied as context to the callbacks.  Returns SPV_SUCCESS on successful
 // parse where the callbacks always return SPV_SUCCESS.  For an invalid parse,
 // returns a status code other than SPV_SUCCESS, and if diagnostic is non-null
-// also emits a diagnostic.  If a callback returns anything other than
+// also emits a diagnostic. If diagnostic is null the context's message consumer
+// will be used to emit any errors. If a callback returns anything other than
 // SPV_SUCCESS, then that status code is returned, no further callbacks are
 // issued, and no additional diagnostics are emitted.
 SPIRV_TOOLS_EXPORT spv_result_t spvBinaryParse(

source/val/validate.cpp

@@ -232,8 +232,15 @@ spv_result_t ValidateBinaryUsingContextAndValidationState(
            << "Invalid SPIR-V.  The id bound is larger than the max id bound "
            << vstate->options()->universal_limits_.max_id_bound << ".";
   }
+
   // Look for OpExtension instructions and register extensions.
-  spvBinaryParse(&context, vstate, words, num_words,
+  // This parse should not produce any error messages. Hijack the context and
+  // replace the message consumer so that we do not pollute any state in input
+  // consumer.
+  spv_context_t hijacked_context = context;
+  hijacked_context.consumer = [](spv_message_level_t, const char*,
+                                 const spv_position_t&, const char*) {};
+  spvBinaryParse(&hijacked_context, vstate, words, num_words,
                  /* parsed_header = */ nullptr, ProcessExtensions,
                  /* diagnostic = */ nullptr);
 

source/val/validation_state.cpp

@@ -197,7 +197,13 @@ ValidationState_t::ValidationState_t(const spv_const_context ctx,
   // fail and generate an error.
   if (num_words > 0) {
     // Count the number of instructions in the binary.
-    spvBinaryParse(ctx, this, words, num_words,
+    // This parse should not produce any error messages. Hijack the context and
+    // replace the message consumer so that we do not pollute any state in input
+    // consumer.
+    spv_context_t hijacked_context = *ctx;
+    hijacked_context.consumer = [](spv_message_level_t, const char*,
+                                   const spv_position_t&, const char*) {};
+    spvBinaryParse(&hijacked_context, this, words, num_words,
                    /* parsed_header = */ nullptr, CountInstructions,
                    /* diagnostic = */ nullptr);
     preallocateStorage();