From 72b5ef6715a2d1d40027f4bcf74d2ed6ce89e443 Mon Sep 17 00:00:00 2001
From: Jiaming Yuan <jm.yuan@outlook.com>
Date: Sat, 27 Sep 2025 07:25:02 +0800
Subject: [PATCH] Fix wasm build.

---
 CMakeLists.txt               |  4 +++-
 cmake/Utils.cmake            | 10 ++++++----
 src/c_api/c_api.cc           |  4 +++-
 src/common/threading_utils.h |  2 +-
 4 files changed, 13 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 41f1b1f48a9c..f8630d670956 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -253,7 +253,9 @@ if(FORCE_COLORED_OUTPUT AND (CMAKE_GENERATOR STREQUAL "Ninja") AND
   set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fdiagnostics-color=always")
 endif()
 
-find_package(Threads REQUIRED)
+if(NOT (CMAKE_SYSTEM_NAME STREQUAL "Emscripten"))
+  find_package(Threads REQUIRED)
+endif()
 
 # -- OpenMP
 include(cmake/FindOpenMPMacOS.cmake)
diff --git a/cmake/Utils.cmake b/cmake/Utils.cmake
index ebc38de68607..50a464f053a1 100644
--- a/cmake/Utils.cmake
+++ b/cmake/Utils.cmake
@@ -261,10 +261,12 @@ endmacro()
 
 # handles dependencies
 macro(xgboost_target_link_libraries target)
-  if(BUILD_STATIC_LIB)
-    target_link_libraries(${target} PUBLIC Threads::Threads ${CMAKE_THREAD_LIBS_INIT})
-  else()
-    target_link_libraries(${target} PRIVATE Threads::Threads ${CMAKE_THREAD_LIBS_INIT})
+  if(NOT (CMAKE_SYSTEM_NAME STREQUAL "Emscripten"))
+    if(BUILD_STATIC_LIB)
+      target_link_libraries(${target} PUBLIC Threads::Threads ${CMAKE_THREAD_LIBS_INIT})
+    else()
+      target_link_libraries(${target} PRIVATE Threads::Threads ${CMAKE_THREAD_LIBS_INIT})
+    endif()
   endif()
 
   if(USE_OPENMP)
diff --git a/src/c_api/c_api.cc b/src/c_api/c_api.cc
index 173856d213d8..75794e49d0c1 100644
--- a/src/c_api/c_api.cc
+++ b/src/c_api/c_api.cc
@@ -1579,7 +1579,9 @@ XGB_DLL int XGBoosterLoadModelFromBuffer(BoosterHandle handle, const void *buf,
   API_BEGIN();
   CHECK_HANDLE();
   xgboost_CHECK_C_ARG_PTR(buf);
-  auto buffer = common::Span<char const>{static_cast<char const *>(buf), len};
+  using CharT = std::add_const_t<char>;
+  using IdxType = common::Span<CharT>::index_type;
+  auto buffer = common::Span{static_cast<CharT *>(buf), static_cast<IdxType>(len)};
   // Don't warn, we have to guess the format with buffer input.
   auto in = DispatchModelType(buffer, "", false);
   common::MemoryFixSizeBuffer fs((void *)buf, len);  // NOLINT(*)
diff --git a/src/common/threading_utils.h b/src/common/threading_utils.h
index 4bbd280a21ee..b20b1bc08069 100644
--- a/src/common/threading_utils.h
+++ b/src/common/threading_utils.h
@@ -267,7 +267,7 @@ void ParallelFor1d(Index size, std::int32_t n_threads, Func&& fn) {
   static_assert(std::is_void_v<std::invoke_result_t<Func, common::Range1d>>);
   auto const n_blocks = DivRoundUp(size, kBlockOfRowsSize);
   common::ParallelFor(n_blocks, n_threads, [&](auto block_id) {
-    auto const block_beg = block_id * kBlockOfRowsSize;
+    std::size_t const block_beg = block_id * kBlockOfRowsSize;
     auto const block_size = std::min(static_cast<std::size_t>(size - block_beg), kBlockOfRowsSize);
     fn(common::Range1d{block_beg, block_beg + block_size});
   });