From 6dcb26d21ed116016f0f3ee7630f532a70a66b79 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Sat, 19 Mar 2022 18:19:44 -0400
Subject: [PATCH] Fix test for whether atomic library is needed

Some platforms need it for atomic<long long> but not for atomic<int>.
---
 CMakeLists.txt         | 7 ++++---
 libqpdf/CMakeLists.txt | 9 +++++++++
 2 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index d58f76c9..33ff69aa 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -154,6 +154,7 @@ if(WIN32 AND NOT SKIP_OS_SECURE_RANDOM)
 endif()
 
 include(CheckCXXSourceCompiles)
+set(ATOMIC_LIBRARY)
 function(check_atomic)
   foreach(I 0 1)
     if(I)
@@ -162,8 +163,8 @@ function(check_atomic)
     check_cxx_source_compiles(
       "#include <atomic>
 int main() {
-    static std::atomic<int> a{0};
-    a = a.fetch_add(1);
+    static std::atomic<unsigned long long> a{0};
+    a = a.fetch_add(1LL);
     return 0;
 }"
       ATOMIC_WORKED${I})
@@ -172,7 +173,7 @@ int main() {
     endif()
   endforeach()
   if(ATOMIC_WORKED1)
-    list(APPEND CMAKE_REQUIRED_LIBRARIES atomic)
+    set(ATOMIC_WORKED1 atomic PARENT_SCOPE)
   endif()
 endfunction()
 check_atomic()
diff --git a/libqpdf/CMakeLists.txt b/libqpdf/CMakeLists.txt
index c5525db2..0875ccd4 100644
--- a/libqpdf/CMakeLists.txt
+++ b/libqpdf/CMakeLists.txt
@@ -410,6 +410,9 @@ target_include_directories(${OBJECT_LIB}
   ${CMAKE_CURRENT_BINARY_DIR})
 target_link_directories(${OBJECT_LIB} INTERFACE ${dep_link_directories})
 target_link_libraries(${OBJECT_LIB} INTERFACE ${dep_link_libraries})
+if(ATOMIC_LIBRARY)
+  target_link_libraries(${OBJECT_LIB} INTERFACE ${ATOMIC_LIBRARY})
+endif()
 
 set(LD_VERSION_FLAGS "")
 function(ld_version_script)
@@ -490,6 +493,9 @@ if(BUILD_SHARED_LIBS)
     $<INSTALL_INTERFACE:include>)
   target_link_directories(${SHARED_LIB} PRIVATE ${dep_link_directories})
   target_link_libraries(${SHARED_LIB} PRIVATE ${dep_link_libraries})
+  if(ATOMIC_LIBRARY)
+    target_link_libraries(${SHARED_LIB} PRIVATE ${ATOMIC_LIBRARY})
+  endif()
   if(LD_VERSION_FLAGS)
     target_link_options(${SHARED_LIB} PRIVATE ${LD_VERSION_FLAGS})
   endif()
@@ -527,6 +533,9 @@ if(BUILD_STATIC_LIBS)
     INTERFACE $<BUILD_INTERFACE:${dep_link_directories}>
     PRIVATE $<INSTALL_INTERFACE:${dep_link_directories}>)
   target_link_libraries(${STATIC_LIB} INTERFACE ${dep_link_libraries})
+  if(ATOMIC_LIBRARY)
+    target_link_libraries(${STATIC_LIB} INTERFACE ${ATOMIC_LIBRARY})
+  endif()
 
   # Avoid name clashes on Windows with the the DLL import library.
   if(NOT DEFINED STATIC_SUFFIX AND BUILD_SHARED_LIBS)