From 579fa4e46f4666eb0fe06b3bcf60ce8a9b5778b7 Mon Sep 17 00:00:00 2001
From: Cory Fields <cory-nospam-@coryfields.com>
Date: Thu, 30 Jan 2025 18:32:39 +0000
Subject: [PATCH 1/2] build: split capnp includes into build/install interfaces
 and mark them as SYSTEM

We're not interested in warnings from Capnp's headers.

The interfaces will be treated differently in the next commit.
---
 CMakeLists.txt | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index de8c95a4..da50e396 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -92,7 +92,15 @@ target_include_directories(multiprocess PUBLIC
   $<BUILD_INTERFACE:${CMAKE_CURRENT_BINARY_DIR}/include>
   $<BUILD_INTERFACE:${CMAKE_CURRENT_SOURCE_DIR}/include>
   $<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
-  ${CAPNP_INCLUDE_DIRECTORY})
+)
+
+target_include_directories(multiprocess SYSTEM PUBLIC
+  $<BUILD_INTERFACE:${CAPNP_INCLUDE_DIRECTORY}>
+)
+target_include_directories(multiprocess SYSTEM PUBLIC
+  $<INSTALL_INTERFACE:${CAPNP_INCLUDE_DIRECTORY}>
+)
+
 target_link_libraries(multiprocess PRIVATE CapnProto::capnp)
 target_link_libraries(multiprocess PRIVATE CapnProto::capnp-rpc)
 target_link_libraries(multiprocess PRIVATE CapnProto::kj)

From 7ac1237ea32aad4a174aaf1958fe2fe0ac129662 Mon Sep 17 00:00:00 2001
From: Cory Fields <cory-nospam-@coryfields.com>
Date: Thu, 30 Jan 2025 18:39:18 +0000
Subject: [PATCH 2/2] build: work around CMake quirk when building as a subdir
 of Bitcoin Core

When building as a subdir of Core and using depends, capnp includes may end up
being installed in a path like:
/dev/bitcoin/depends/HOST/include

It then detects that the install interface has been given an absolute path
inside of the project dir:
/dev/bitcoin/

In that case it throws an error because it wants paths within the project to
always be relative.

This shouldn't matter *at all* because we're never actually going to install
the lib anyway, but CMake populates the install interface despite the
EXCLUDE_FROM_ALL property being set.

Since other projects may wish to include libmultiprocess as a subdir and also
install it, don't use the subdir condition to check for this case. Instead,
test for the EXCLUDE_FROM_ALL on the directory, as if that's set, the parent
project won't be installing.
---
 CMakeLists.txt | 15 ++++++++++++---
 1 file changed, 12 insertions(+), 3 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index da50e396..24049e08 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -97,9 +97,18 @@ target_include_directories(multiprocess PUBLIC
 target_include_directories(multiprocess SYSTEM PUBLIC
   $<BUILD_INTERFACE:${CAPNP_INCLUDE_DIRECTORY}>
 )
-target_include_directories(multiprocess SYSTEM PUBLIC
-  $<INSTALL_INTERFACE:${CAPNP_INCLUDE_DIRECTORY}>
-)
+
+# Hack to avoid exporting a path "which is prefixed in the source directory".
+# If we're in another project's subdir and capnp is installed somewhere inside
+# that project (as it is with depends in Bicoin Core) CMake refuses to allow it
+# in the install interface. Use the "EXCLUDE_FROM_ALL" property as a proxy for
+# detecting this condition, as in that case install won't happen anyway.
+get_directory_property(mp_skip_install EXCLUDE_FROM_ALL)
+if(NOT "${mp_skip_install}")
+  target_include_directories(multiprocess SYSTEM PUBLIC
+    $<INSTALL_INTERFACE:${CAPNP_INCLUDE_DIRECTORY}>
+  )
+endif()
 
 target_link_libraries(multiprocess PRIVATE CapnProto::capnp)
 target_link_libraries(multiprocess PRIVATE CapnProto::capnp-rpc)