Remove 32-bit limitation (#2388)

* Remove 32-bit limitation

* Fix build problems

* Add 32-bit disclaimer and fix MSVC x86 warnings

- Move 32-bit warning to top of README with strong disclaimer
- Add static_cast<size_t> to fix truncation warnings on 32-bit MSVC

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.github/workflows/test-32bit.yml

@@ -0,0 +1,36 @@
+name: 32-bit Build Test
+
+on:
+  push:
+    branches: [master]
+  pull_request:
+    branches: [master]
+  workflow_dispatch:
+
+concurrency:
+  group: ${{ github.workflow }}-${{ github.ref || github.run_id }}
+  cancel-in-progress: true
+
+jobs:
+  test-win32:
+    name: Windows 32-bit (MSVC x86)
+    runs-on: windows-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Build (Win32)
+        shell: cmd
+        run: |
+          call "C:\Program Files\Microsoft Visual Studio\2022\Enterprise\VC\Auxiliary\Build\vcvarsall.bat" x86
+          cl /std:c++14 /EHsc /W4 /WX /c /Fo:NUL test\test_32bit_build.cpp
+
+  test-arm32:
+    name: ARM 32-bit (cross-compile)
+    runs-on: ubuntu-latest
+    timeout-minutes: 10
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install cross compiler
+        run: sudo apt-get update && sudo apt-get install -y g++-arm-linux-gnueabihf
+      - name: Build (ARM 32-bit)
+        run: arm-linux-gnueabihf-g++ -std=c++11 -Wall -Wextra -Wno-psabi -Werror -c -o /dev/null test/test_32bit_build.cpp

.github/workflows/test.yaml

@@ -40,7 +40,7 @@ jobs:
           clang-format --version
           cd test && make style_check
 
-  build-error-check-on-32bit:
+  build-and-test-on-32bit:
     runs-on: ubuntu-latest
     if: >
       (github.event_name == 'push') ||
@@ -64,9 +64,8 @@ jobs:
             libssl-dev${{ matrix.config.arch_suffix }} libcurl4-openssl-dev${{ matrix.config.arch_suffix }} \
             zlib1g-dev${{ matrix.config.arch_suffix }} libbrotli-dev${{ matrix.config.arch_suffix }} \
             libzstd-dev${{ matrix.config.arch_suffix }}
-      - name: build and run tests (expect failure)
+      - name: build and run tests
         run: cd test && make test EXTRA_CXXFLAGS="${{ matrix.config.arch_flags }}"
-        continue-on-error: true
 
   ubuntu:
     runs-on: ubuntu-latest