From db397f441997f975b07fe0c09ca5a85d0970e4b7 Mon Sep 17 00:00:00 2001
From: Allison Piper <alliepiper16@gmail.com>
Date: Mon, 28 Oct 2024 13:39:40 -0400
Subject: [PATCH] Check for missing `inline` on functions in public headers.
 (#2570)

* Check for missing `inline` on functions in public headers.

We can test for missing `inline` markup by linking the header objects into the same target twice.
By default CMake will eliminate duplicate link targets, but linking both the target and the $<TARGET_OBJECTS:target> bypasses the duplicate checks.

* Add -fPIC, formatting.

* Switch link_check to executable to avoid -fPIC issues
---
 cmake/CCCLGenerateHeaderTests.cmake | 12 ++++++++++++
 cmake/link_check_main.cpp           |  4 ++++
 2 files changed, 16 insertions(+)
 create mode 100644 cmake/link_check_main.cpp

diff --git a/cmake/CCCLGenerateHeaderTests.cmake b/cmake/CCCLGenerateHeaderTests.cmake
index e483b194513..9371cbaa7d7 100644
--- a/cmake/CCCLGenerateHeaderTests.cmake
+++ b/cmake/CCCLGenerateHeaderTests.cmake
@@ -108,4 +108,16 @@ function(cccl_generate_header_tests target_name project_include_path)
   add_library(${target_name} OBJECT ${header_srcs})
   cccl_configure_target(${target_name} ${cccl_configure_target_options})
 
+  # Check that all functions in headers are either template functions or inline:
+  set(link_target ${target_name}.link_check)
+  add_executable(${link_target} "${CCCL_SOURCE_DIR}/cmake/link_check_main.cpp")
+  cccl_configure_target(${link_target} ${cccl_configure_target_options})
+  # Linking both ${target_name} and $<TARGET_OBJECTS:${target_name}> forces CMake to
+  # link the same objects twice. The compiler will complain about duplicate symbols if
+  # any functions are missing inline markup.
+  target_link_libraries(${link_target} PRIVATE
+    ${target_name}
+    $<TARGET_OBJECTS:${target_name}>
+  )
+
 endfunction()
diff --git a/cmake/link_check_main.cpp b/cmake/link_check_main.cpp
new file mode 100644
index 00000000000..f8b643afbf2
--- /dev/null
+++ b/cmake/link_check_main.cpp
@@ -0,0 +1,4 @@
+int main()
+{
+  return 0;
+}