From cf773aaa13364edc53a14aed1fee9a22112e9fec Mon Sep 17 00:00:00 2001
From: Daeho Ro <40587651+daeho-ro@users.noreply.github.com>
Date: Sun, 12 Jul 2026 19:48:47 +0900
Subject: [PATCH] cmake: allow system fmt/tomlplusplus/boost for bundled deps

FetchContent now tries find_package() first for fmt, tomlplusplus and
Boost.Regex, only falling back to the vendored copies when no system
package is found. This lets distribution and package-manager builds
(e.g. Homebrew) link against system libraries instead of the bundles,
without changing the default behaviour for a plain source build.
---
 libs/CMakeLists.txt | 50 +++++++++++++++++++++++++++------------------
 1 file changed, 30 insertions(+), 20 deletions(-)

diff --git a/libs/CMakeLists.txt b/libs/CMakeLists.txt
index 5ea08ef9d..c3aa97d40 100644
--- a/libs/CMakeLists.txt
+++ b/libs/CMakeLists.txt
@@ -9,33 +9,43 @@ add_subdirectory(sha1)
 add_subdirectory(subcircuit)
 block()
     set(BUILD_SHARED_LIBS OFF)
+    set(CMAKE_FIND_PACKAGE_TARGETS_GLOBAL TRUE)
     include(FetchContent)
     set(FETCHCONTENT_FULLY_DISCONNECTED ON)
 
     option(FMT_INSTALL OFF)
-    FetchContent_Declare(
-        fmt
-        EXCLUDE_FROM_ALL
-        SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/fmt
-    )
-    FetchContent_MakeAvailable(fmt)
+    find_package(fmt QUIET)
+    if(NOT fmt_FOUND)
+        FetchContent_Declare(
+            fmt
+            EXCLUDE_FROM_ALL
+            SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/fmt
+        )
+        FetchContent_MakeAvailable(fmt)
+    endif()
 
-    FetchContent_Declare(
-        tomlplusplus
-        EXCLUDE_FROM_ALL
-        SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/tomlplusplus
-    )
-    FetchContent_MakeAvailable(tomlplusplus)
-
-    FetchContent_Declare(
-        boost_regex
-        EXCLUDE_FROM_ALL
-        SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/boost_regex
-        SOURCE_SUBDIR _no_build_
-    )
-    FetchContent_MakeAvailable(boost_regex)
+    find_package(tomlplusplus QUIET)
+    if(NOT tomlplusplus_FOUND)
+        FetchContent_Declare(
+            tomlplusplus
+            EXCLUDE_FROM_ALL
+            SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/tomlplusplus
+        )
+        FetchContent_MakeAvailable(tomlplusplus)
+    endif()
 
     if (NOT YOSYS_WITHOUT_SLANG)
+        find_package(Boost QUIET COMPONENTS regex)
+        if(NOT Boost_FOUND)
+            FetchContent_Declare(
+                boost_regex
+                EXCLUDE_FROM_ALL
+                SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}/boost_regex
+                SOURCE_SUBDIR _no_build_
+            )
+            FetchContent_MakeAvailable(boost_regex)
+        endif()
+
         set(SLANG_USE_MIMALLOC OFF)
         add_subdirectory(slang)
         # Headers autodetect based on <boost/config.hpp> but when version