Implement to_string(uint32_t) without using the locale

Using the locale takes a mutex deep in the C++ library.
Avoid this on hot compilation paths, e.g. in the validator.

Fixed: KhronosGroup#5802

Android.mk

@@ -27,6 +27,7 @@ SPVTOOLS_SRC_FILES := \
 		source/table.cpp \
 		source/text.cpp \
 		source/text_handler.cpp \
+		source/to_string.cpp \
 		source/util/bit_vector.cpp \
 		source/util/parse_number.cpp \
 		source/util/string_utils.cpp \

BUILD.gn

@@ -475,6 +475,8 @@ static_library("spvtools") {
     "source/text.h",
     "source/text_handler.cpp",
     "source/text_handler.h",
+    "source/to_string.cpp",
+    "source/to_string.h",
     "source/util/bit_vector.cpp",
     "source/util/bit_vector.h",
     "source/util/bitutils.h",

source/CMakeLists.txt

@@ -266,6 +266,7 @@ set(SPIRV_SOURCES
   ${CMAKE_CURRENT_SOURCE_DIR}/table.h
   ${CMAKE_CURRENT_SOURCE_DIR}/text.h
   ${CMAKE_CURRENT_SOURCE_DIR}/text_handler.h
+  ${CMAKE_CURRENT_SOURCE_DIR}/to_string.h
   ${CMAKE_CURRENT_SOURCE_DIR}/val/validate.h
 
   ${CMAKE_CURRENT_SOURCE_DIR}/util/bit_vector.cpp
@@ -294,6 +295,7 @@ set(SPIRV_SOURCES
   ${CMAKE_CURRENT_SOURCE_DIR}/table.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/text.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/text_handler.cpp
+  ${CMAKE_CURRENT_SOURCE_DIR}/to_string.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/val/validate.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/val/validate_adjacency.cpp
   ${CMAKE_CURRENT_SOURCE_DIR}/val/validate_annotation.cpp

source/name_mapper.cpp

@@ -25,24 +25,15 @@
 #include "source/binary.h"
 #include "source/latest_version_spirv_header.h"
 #include "source/parsed_operand.h"
+#include "source/to_string.h"
 #include "spirv-tools/libspirv.h"
 
 namespace spvtools {
-namespace {
 
-// Converts a uint32_t to its string decimal representation.
-std::string to_string(uint32_t id) {
-  // Use stringstream, since some versions of Android compilers lack
-  // std::to_string.
-  std::stringstream os;
-  os << id;
-  return os.str();
+NameMapper GetTrivialNameMapper() {
+  return [](uint32_t i) { return spvtools::to_string(i); };
 }
 
-}  // anonymous namespace
-
-NameMapper GetTrivialNameMapper() { return to_string; }
-
 FriendlyNameMapper::FriendlyNameMapper(const spv_const_context context,
                                        const uint32_t* code,
                                        const size_t wordCount)

source/opt/inst_debug_printf_pass.cpp

@@ -17,6 +17,7 @@
 #include "inst_debug_printf_pass.h"
 
 #include "source/spirv_constant.h"
+#include "source/to_string.h"
 #include "source/util/string_utils.h"
 #include "spirv/unified1/NonSemanticDebugPrintf.h"
 
@@ -396,7 +397,7 @@ uint32_t InstDebugPrintfPass::GetStreamWriteFunctionId(uint32_t param_cnt) {
     context()->AddFunction(std::move(output_func));
 
     std::string name("stream_write_");
-    name += std::to_string(param_cnt);
+    name += spvtools::to_string(param_cnt);
 
     context()->AddDebug2Inst(
         NewGlobalName(param2output_func_id_[param_cnt], name));

source/to_string.cpp

@@ -0,0 +1,40 @@
+// Copyright (c) 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "source/to_string.h"
+
+#include <cassert>
+
+namespace spvtools {
+
+std::string to_string(uint32_t n) {
+  constexpr int max_digits = 10;  // max uint has 10 digits
+  // Contains the resulting digits, with least significant digit in the last
+  // entry.
+  char buf[max_digits];
+  int write_index = max_digits - 1;
+  if (n == 0) {
+    buf[write_index] = '0';
+  } else {
+    while (n > 0) {
+      int units = n % 10;
+      buf[write_index--] = "0123456789"[units];
+      n = (n - units) / 10;
+    }
+    write_index++;
+  }
+  assert(write_index >= 0);
+  return std::string(buf + write_index, max_digits - write_index);
+}
+}  // namespace spvtools

source/to_string.h

@@ -0,0 +1,29 @@
+// Copyright (c) 2024 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef SOURCE_TO_STRING_H_
+#define SOURCE_TO_STRING_H_
+
+#include <cstdint>
+#include <string>
+
+namespace spvtools {
+
+// Returns the decimal representation of a number as a string.
+// Ignores the locale.
+std::string to_string(uint32_t n);
+
+}  // namespace spvtools
+
+#endif  // SOURCE_TO_STRING_H_