From 61daf8f14377a192598fe42b912cc5cdc1900918 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Sat, 19 Apr 2025 16:08:07 -0400
Subject: [PATCH] Fix android build issues (fixes #950)

---
 .github/workflows/main.yml      |  1 +
 build-scripts/build-android-ndk | 41 +++++++++++++++++++++++++++++++++++++++++
 libqpdf/CMakeLists.txt          | 11 +++++------
 3 files changed, 47 insertions(+), 6 deletions(-)
 create mode 100755 build-scripts/build-android-ndk

diff --git a/.github/workflows/main.yml b/.github/workflows/main.yml
index 8fe8acd..31bf9a0 100644
--- a/.github/workflows/main.yml
+++ b/.github/workflows/main.yml
@@ -163,6 +163,7 @@ jobs:
           - test-alt-zlib
           - test-unsigned-char
           - test-c++-next
+          - build-android-ndk
     steps:
       - uses: actions/checkout@v4
       - name: ${{ matrix.script }}
diff --git a/build-scripts/build-android-ndk b/build-scripts/build-android-ndk
new file mode 100755
index 0000000..0650357
--- /dev/null
+++ b/build-scripts/build-android-ndk
@@ -0,0 +1,41 @@
+#!/bin/bash
+set -xeo pipefail
+cd $(dirname $0)/..
+
+# Build a static libqpdf for android with an ABI version <= 24. This
+# is just to exercise that configuring for that platform works.
+
+declare -a android_flags
+android_flags=( \
+      -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake" \
+      -DANDROID_ABI=armeabi-v7a \
+      -DANDROID_PLATFORM=android-21 \
+)
+
+rm -rf android-work build-android
+mkdir android-work
+pushd android-work
+export WORK=$PWD
+git clone https://github.com/libjpeg-turbo/libjpeg-turbo
+cd libjpeg-turbo
+cmake -S . -B build \
+      "${android_flags[@]}" \
+      -DCMAKE_INSTALL_PREFIX="$WORK" \
+      -DENABLE_STATIC=ON \
+      -DENABLE_SHARED=OFF \
+      -DCMAKE_POSITION_INDEPENDENT_CODE=ON
+make -C build -j$(nproc)
+make -C build install
+popd
+
+export CMAKE_PREFIX_PATH=$WORK LDFLAGS="-L$WORK/lib"
+cmake -S . -B build-android \
+      "${android_flags[@]}" \
+      -DCMAKE_BUILD_TYPE=RelWithDebinfo \
+      -DUSE_IMPLICIT_CRYPTO=OFF \
+      -DBUILD_SHARED_LIBS=OFF \
+      -DBUILD_STATIC_LIBS=ON \
+      -DREQUIRE_CRYPTO_NATIVE=ON
+
+cmake --build build-android -t libqpdf --verbose -j$(nproc) -- -k
+file build-android/libqpdf/CMakeFiles/libqpdf_object.dir/QUtil.cc.o | grep 'ARM, EABI5'
diff --git a/libqpdf/CMakeLists.txt b/libqpdf/CMakeLists.txt
index 371cd6b..12d7018 100644
--- a/libqpdf/CMakeLists.txt
+++ b/libqpdf/CMakeLists.txt
@@ -349,7 +349,11 @@ int main(int argc, char* argv[]) {
     LFS_WITHOUT_MACROS)
 
 check_c_source_compiles(
-"#define _FILE_OFFSET_BITS 64
+"#if !(defined(__ANDROID__) && __ANDROID_API__ <= 24)
+// Defining _FILE_OFFSET_BITS on Android <= 24 is known to
+// produce incorrect results.
+#define _FILE_OFFSET_BITS 64
+#endif
 #include <stdio.h>
 #include <sys/types.h>
 int main(int argc, char* argv[]) {
@@ -359,11 +363,6 @@ int main(int argc, char* argv[]) {
 if(LFS_WITH_MACROS AND NOT LFS_WITHOUT_MACROS)
   set(_FILE_OFFSET_BITS 64)
 endif()
-
-# fseeko may not exist with _FILE_OFFSET_BITS=64 but can exist with
-# _FILE_OFFSET_BITS unset or 32 (e.g. Android ARMv7 with NDK 26b and
-# API level < 24) so we need to test fseeko after testing for
-# _FILE_OFFSET_BITS. See https://github.com/qpdf/qpdf/issues/950.
 check_symbol_exists(fseeko "stdio.h" HAVE_FSEEKO)
 check_symbol_exists(fseeko64 "stdio.h" HAVE_FSEEKO64)
 
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