From 620f297f311718f3d186b716676779e046e3255c Mon Sep 17 00:00:00 2001
From: Ryan Ofsky <ryan@ofsky.org>
Date: Wed, 3 Jun 2026 17:04:59 -0400
Subject: [PATCH 1/2] cmake: make target_capnp_sources use CURRENT dirs

TargetCapnpSources.cmake computed the build-side include directory by
computing file(RELATIVE_PATH) from CMAKE_SOURCE_DIR to include_prefix
and appending the result to CMAKE_BINARY_DIR. This assumes include_prefix
is inside CMAKE_SOURCE_DIR, which holds when master is the top-level
cmake project but breaks when it is added as a subdirectory of an external
project (e.g. the support branch) whose source root is elsewhere.

In that case the relative path contains ".." and the resulting
build_include_prefix points to a nonexistent directory instead of
CMAKE_CURRENT_BINARY_DIR where the generated headers actually live.

Fix by anchoring on CMAKE_CURRENT_SOURCE_DIR / CMAKE_CURRENT_BINARY_DIR
instead of the top-level CMAKE_SOURCE_DIR/BINARY_DIR. Since cmake
mirrors source-tree structure into the binary tree, the mapping is
equivalent for any include_prefix inside CMAKE_SOURCE_DIR, and correct
for paths outside it.

Also update docstring and example to use CMAKE_CURRENT_SOURCE_DIR.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 cmake/TargetCapnpSources.cmake | 14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

diff --git a/cmake/TargetCapnpSources.cmake b/cmake/TargetCapnpSources.cmake
index abcca70f..fe4bca9a 100644
--- a/cmake/TargetCapnpSources.cmake
+++ b/cmake/TargetCapnpSources.cmake
@@ -27,10 +27,8 @@ Arguments:
 
       #include <schema.capnp.h>
 
-    The specified include_prefix should be ${CMAKE_SOURCE_DIR} or a
-    subdirectory of it to include files relative to the project root. It can
-    be ${CMAKE_CURRENT_SOURCE_DIR} to include files relative to the current
-    source directory.
+    Pass ${CMAKE_CURRENT_SOURCE_DIR} or a subdirectory of it to include files
+    relative to the current source directory (the typical usage).
 
 Additional Unnamed Arguments:
 
@@ -46,9 +44,9 @@ Optional Keyword Arguments:
 Example:
   # Assuming `my_library` is a target and `lib/` contains `.capnp` schema
   # files with imports from `include/`.
-  target_capnp_sources(my_library "${CMAKE_SOURCE_DIR}"
+  target_capnp_sources(my_library "${CMAKE_CURRENT_SOURCE_DIR}"
                        lib/schema1.capnp lib/schema2.capnp
-                       IMPORT_PATHS ${CMAKE_SOURCE_DIR}/include)
+                       IMPORT_PATHS ${CMAKE_CURRENT_SOURCE_DIR}/include)
 
 #]=]
 
@@ -98,8 +96,8 @@ function(target_capnp_sources target include_prefix)
 
   # Translate include_prefix from a source path to a binary path and add it as a
   # target include directory.
-  set(build_include_prefix ${CMAKE_BINARY_DIR})
-  file(RELATIVE_PATH relative_path ${CMAKE_SOURCE_DIR} ${include_prefix})
+  set(build_include_prefix ${CMAKE_CURRENT_BINARY_DIR})
+  file(RELATIVE_PATH relative_path ${CMAKE_CURRENT_SOURCE_DIR} ${include_prefix})
   if(relative_path)
     string(APPEND build_include_prefix "/" "${relative_path}")
   endif()

From 615a94fe3a213380eb50cde82e4b4d718bf63dd5 Mon Sep 17 00:00:00 2001
From: Ryan Ofsky <ryan@ofsky.org>
Date: Thu, 4 Jun 2026 14:49:18 -0400
Subject: [PATCH 2/2] cmake: document ONLY_CAPNP option in target_capnp_sources

The ONLY_CAPNP keyword was parsed but not mentioned in the function's
docstring. Add a description explaining what it does and when to use it.

Suggested by hebasto in
https://github.com/bitcoin-core/libmultiprocess/pull/289#pullrequestreview-4427856835

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
---
 cmake/TargetCapnpSources.cmake | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/cmake/TargetCapnpSources.cmake b/cmake/TargetCapnpSources.cmake
index fe4bca9a..f04a9657 100644
--- a/cmake/TargetCapnpSources.cmake
+++ b/cmake/TargetCapnpSources.cmake
@@ -41,6 +41,13 @@ Optional Keyword Arguments:
   IMPORT_PATHS: Specifies additional directories to search for imported
     `.capnp` files.
 
+  ONLY_CAPNP: If specified, only the Cap'n Proto serialization files
+    (`.capnp.h`, `.capnp.c++`) are generated and compiled. The mpgen proxy
+    files (`.capnp.proxy-client.c++`, `.capnp.proxy-server.c++`,
+    `.capnp.proxy-types.c++`, etc.) are skipped. Useful when you need
+    Cap'n Proto serialization without the multiprocess RPC proxy
+    infrastructure.
+
 Example:
   # Assuming `my_library` is a target and `lib/` contains `.capnp` schema
   # files with imports from `include/`.