add fmt

fmt is a formatting library for C++. It has several properties that make it nice
for inclusion in PyTorch:
- Widely used
- Basically copies how Python does it
- Support for all the compilers and platforms we care about
- Standards track (C++20)
- Small code size
- Header only
- The author works at FB (hi @vitaut).

This PR includes it as a submodule and sets up the build. It also
provides some example usage, including a `TORCH_CHECK_FMT` macro in c10
that should test all the builds we care about.

ghstack-source-id: cbae4e082d4af37a3c0e34e69987dcbab41f57e6
Pull Request resolved: #37241

.gitmodules

@@ -122,3 +122,7 @@
     ignore = dirty
     path = third_party/XNNPACK
     url = https://github.com/google/XNNPACK.git
+[submodule "third_party/fmt"]
+    ignore = dirty
+    path = third_party/fmt
+    url = https://github.com/fmtlib/fmt.git

BUILD.bazel

@@ -1738,6 +1738,7 @@ cc_library(
         "@foxi",
         "@gloo",
         "@onnx",
+        "@fmt",
     ] + if_cuda(
         [
             ":caffe2_cpp_cuda",

WORKSPACE

@@ -113,6 +113,12 @@ new_local_repository(
     path = "third_party/sleef",
 )
 
+new_local_repository(
+    name = "fmt",
+    build_file = "//third_party:fmt.BUILD",
+    path = "third_party/fmt",
+)
+
 new_patched_local_repository(
     name = "tbb",
     patches = [

cmake/Dependencies.cmake

@@ -596,7 +596,7 @@ if(USE_FBGEMM)
   caffe2_update_option(USE_FBGEMM ON)
 else()
   caffe2_update_option(USE_FBGEMM OFF)
-  message(WARNING 
+  message(WARNING
     "Turning USE_FAKELOWP off as it depends on USE_FBGEMM.")
   caffe2_update_option(USE_FAKELOWP OFF)
 endif()
@@ -1552,3 +1552,28 @@ endif()
 #
 # End ATen checks
 #
+
+# Override install location of `fmt` libs.
+#
+# `fmt` uses CMAKE_INSTALL_LIBDIR to determine where to put libraries. PyTorch
+# somewhat misbehaves and installs everything to TORCH_INSTALL_LIB_DIR. For
+# consistency, make `fmt` do the same thing by temporarily overriding
+# CMAKE_INSTALL_LIBDIR.
+set(OLD_CMAKE_INSTALL_LIBDIR ${CMAKE_INSTALL_LIBDIR})
+set(CMAKE_INSTALL_LIBDIR ${TORCH_INSTALL_LIB_DIR})
+
+set(FMT_INSTALL ON CACHE BOOL " " FORCE)
+add_subdirectory(${CMAKE_SOURCE_DIR}/third_party/fmt)
+
+set(CMAKE_INSTALL_LIBDIR ${OLD_CMAKE_INSTALL_LIBDIR})
+
+# Disable compiler feature checks for `fmt`.
+#
+# CMake compiles a little program to check compiler features. Some of our build
+# configurations (notably the mobile build analyzer) will populate
+# CMAKE_CXX_FLAGS in ways that break feature checks. Since we already know
+# `fmt` is compatible with a superset of the compilers that PyTorch is, it
+# shouldn't be too bad to just disable the checks.
+set_target_properties(fmt PROPERTIES INTERFACE_COMPILE_FEATURES "")
+
+list(APPEND Caffe2_DEPENDENCY_LIBS fmt::fmt)

cmake/TorchConfig.cmake.in

@@ -54,6 +54,9 @@ if(NOT @BUILD_SHARED_LIBS@)
   find_library(TORCH_CPU_LIBRARY torch_cpu PATHS "${TORCH_INSTALL_PREFIX}/lib")
   list(APPEND TORCH_LIBRARIES ${TORCH_CPU_LIBRARY})
 
+  find_library(FMT_LIBRARY fmt PATHS "${TORCH_INSTALL_PREFIX}/lib")
+  list(APPEND TORCH_LIBRARIES ${FMT_LIBRARY})
+
   if(@USE_NNPACK@)
     find_library(NNPACK_LIBRARY nnpack PATHS "${TORCH_INSTALL_PREFIX}/lib")
     list(APPEND TORCH_LIBRARIES ${NNPACK_LIBRARY})

ios/TestApp/benchmark/setup.rb

@@ -63,7 +63,7 @@
     target.resources_build_phase.add_file_reference(config_file_ref, true)
 end
 puts "Linking static libraries..."
-libs = ['libc10.a', 'libclog.a', 'libnnpack.a', 'libXNNPACK.a', 'libeigen_blas.a', 'libcpuinfo.a', 'libpytorch_qnnpack.a', 'libtorch_cpu.a', 'libtorch.a']
+libs = ['libc10.a', 'libclog.a', 'libnnpack.a', 'libXNNPACK.a', 'libeigen_blas.a', 'libcpuinfo.a', 'libpytorch_qnnpack.a', 'libtorch_cpu.a', 'libtorch.a', 'libfmt.a']
 targets.each do |target|
     target.frameworks_build_phases.clear
     for lib in libs do

scripts/xcode_build.rb

@@ -51,7 +51,7 @@
 
 # link static libraries
 target.frameworks_build_phases.clear
-libs = ['libc10.a', 'libclog.a', 'libnnpack.a', 'libXNNPACK.a', 'libeigen_blas.a', 'libcpuinfo.a', 'libpytorch_qnnpack.a', 'libtorch_cpu.a', 'libtorch.a']
+libs = ['libc10.a', 'libclog.a', 'libnnpack.a', 'libXNNPACK.a', 'libeigen_blas.a', 'libcpuinfo.a', 'libpytorch_qnnpack.a', 'libtorch_cpu.a', 'libtorch.a', 'libfmt.a']
 for lib in libs do
     path = "#{install_path}/lib/#{lib}"
     if File.exist?(path)

third_party/fmt.BUILD

@@ -0,0 +1,9 @@
+load("@rules_cc//cc:defs.bzl", "cc_library")
+
+cc_library(
+    name = "fmt",
+    hdrs = glob(["include/fmt/*.h",]),
+    srcs = glob(["src/*.cc",]),
+    includes = ["include"],
+    visibility = ["//visibility:public"],
+)

torch/csrc/jit/serialization/import.cpp

@@ -17,6 +17,7 @@
 #include <caffe2/serialize/istream_adapter.h>
 
 #include <ATen/ATen.h>
+#include <fmt/core.h>
 
 #include <fstream>
 #include <string>
@@ -44,12 +45,11 @@ void postSetStateValidate(const IValue& v) {
     if (attrType->kind() != TypeKind::OptionalType) {
       TORCH_CHECK(
           !slot.isNone(),
-          "The field '",
-          attrName,
-          "' was left unitialized after __setstate__, but expected a ",
-          "value of type '",
-          attrType->python_str(),
-          "'");
+          fmt::format(
+              "The field '{}' was left uninitialized after '__setstate__', "
+              "but expected a value of type '{}'",
+              attrName,
+              attrType->python_str()));
     }
   }
 }