[Lldb-commits] [lldb] [lldb] Add Flang as an optional dependency in LLDB (PR #207764)

Wed Jul 8 05:53:44 PDT 2026

https://github.com/Iasonaskrpr updated https://github.com/llvm/llvm-project/pull/207764

>From c94bc02707b56671dfe25e76eb4ca634cf6d2132 Mon Sep 17 00:00:00 2001
From: Iasonaskrpr <iaskarapro at gmail.com>
Date: Mon, 6 Jul 2026 18:06:32 +0300
Subject: [PATCH 1/4] [lldb][Fortran] Added CMAKE variable guard for Fortran
 support in LLDB

---
 lldb/cmake/modules/FindFlang.cmake  | 17 +++++++++++++++++
 lldb/cmake/modules/LLDBConfig.cmake |  1 +
 2 files changed, 18 insertions(+)
 create mode 100644 lldb/cmake/modules/FindFlang.cmake

diff --git a/lldb/cmake/modules/FindFlang.cmake b/lldb/cmake/modules/FindFlang.cmake
new file mode 100644
index 0000000000000..f71d42c5fb586
--- /dev/null
+++ b/lldb/cmake/modules/FindFlang.cmake
@@ -0,0 +1,17 @@
+# FindFlang.cmake
+
+include(FindPackageHandleStandardArgs)
+
+# If Flang and lldb are in-tree then the libraries will already be available, otherwise look for specific directories
+if(TARGET flangFrontEnd)
+  set(Flang_FOUND TRUE)
+else()
+  find_package(Flang QUIET CONFIG HINTS ${Flang_DIR} ${LLVM_DIR}/../flang)
+endif()
+
+find_package_handle_standard_args(Flang
+  FOUND_VAR
+    Flang_FOUND
+  REQUIRED_VARS
+    Flang_FOUND
+)
\ No newline at end of file
diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
index e086aaf5d3632..82ad8b19ebb79 100644
--- a/lldb/cmake/modules/LLDBConfig.cmake
+++ b/lldb/cmake/modules/LLDBConfig.cmake
@@ -64,6 +64,7 @@ add_optional_dependency(LLDB_ENABLE_LUA "Enable Lua scripting support in LLDB" L
 add_optional_dependency(LLDB_ENABLE_PYTHON "Enable Python scripting support in LLDB" PythonAndSwig PYTHONANDSWIG_FOUND)
 add_optional_dependency(LLDB_ENABLE_LIBXML2 "Enable Libxml 2 support in LLDB" LibXml2 LIBXML2_FOUND VERSION ${LLDB_LIBXML2_VERSION})
 add_optional_dependency(LLDB_ENABLE_TREESITTER "Enable Tree-sitter syntax highlighting" TreeSitter TREESITTER_FOUND)
+add_optional_dependency(LLDB_ENABLE_FORTRAN "Enable Fortran support in lldb" Flang Flang_FOUND)
 
 option(LLDB_USE_ENTITLEMENTS "When codesigning, use entitlements if available" ON)
 option(LLDB_BUILD_FRAMEWORK "Build LLDB.framework (Darwin only)" OFF)

>From 569e29d532ebf858728e4b79cfb93fd827f4dc16 Mon Sep 17 00:00:00 2001
From: Iasonaskrpr <iaskarapro at gmail.com>
Date: Mon, 6 Jul 2026 22:14:20 +0300
Subject: [PATCH 2/4] [lldb] Removed support for out-of-tree flang builds

---
 lldb/cmake/modules/FindFlang.cmake  | 17 -----------------
 lldb/cmake/modules/LLDBConfig.cmake |  9 ++++++++-
 2 files changed, 8 insertions(+), 18 deletions(-)
 delete mode 100644 lldb/cmake/modules/FindFlang.cmake

diff --git a/lldb/cmake/modules/FindFlang.cmake b/lldb/cmake/modules/FindFlang.cmake
deleted file mode 100644
index f71d42c5fb586..0000000000000
--- a/lldb/cmake/modules/FindFlang.cmake
+++ /dev/null
@@ -1,17 +0,0 @@
-# FindFlang.cmake
-
-include(FindPackageHandleStandardArgs)
-
-# If Flang and lldb are in-tree then the libraries will already be available, otherwise look for specific directories
-if(TARGET flangFrontEnd)
-  set(Flang_FOUND TRUE)
-else()
-  find_package(Flang QUIET CONFIG HINTS ${Flang_DIR} ${LLVM_DIR}/../flang)
-endif()
-
-find_package_handle_standard_args(Flang
-  FOUND_VAR
-    Flang_FOUND
-  REQUIRED_VARS
-    Flang_FOUND
-)
\ No newline at end of file
diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
index 82ad8b19ebb79..ffb01342531dc 100644
--- a/lldb/cmake/modules/LLDBConfig.cmake
+++ b/lldb/cmake/modules/LLDBConfig.cmake
@@ -56,6 +56,14 @@ set(LLDB_LIBXML2_VERSION "2.8" CACHE STRING
   static builds of libxml 2. Use at your own risk.")
 mark_as_advanced(LLDB_LIBXML2_VERSION)
 
+set(LLDB_DEFAULT_ENABLE_FORTRAN OFF)
+
+if("flang" IN_LIST LLVM_ENABLE_PROJECTS)
+  set(LLDB_DEFAULT_ENABLE_FORTRAN ON)
+endif()
+
+option(LLDB_ENABLE_FORTRAN "Enable Fortran support in LLDB" ${LLDB_DEFAULT_ENABLE_FORTRAN})
+
 add_optional_dependency(LLDB_ENABLE_SWIG "Enable SWIG to generate LLDB bindings" SWIG SWIG_FOUND VERSION 4)
 add_optional_dependency(LLDB_ENABLE_LIBEDIT "Enable editline support in LLDB" LibEdit LibEdit_FOUND)
 add_optional_dependency(LLDB_ENABLE_CURSES "Enable curses support in LLDB" CursesAndPanel CURSESANDPANEL_FOUND)
@@ -64,7 +72,6 @@ add_optional_dependency(LLDB_ENABLE_LUA "Enable Lua scripting support in LLDB" L
 add_optional_dependency(LLDB_ENABLE_PYTHON "Enable Python scripting support in LLDB" PythonAndSwig PYTHONANDSWIG_FOUND)
 add_optional_dependency(LLDB_ENABLE_LIBXML2 "Enable Libxml 2 support in LLDB" LibXml2 LIBXML2_FOUND VERSION ${LLDB_LIBXML2_VERSION})
 add_optional_dependency(LLDB_ENABLE_TREESITTER "Enable Tree-sitter syntax highlighting" TreeSitter TREESITTER_FOUND)
-add_optional_dependency(LLDB_ENABLE_FORTRAN "Enable Fortran support in lldb" Flang Flang_FOUND)
 
 option(LLDB_USE_ENTITLEMENTS "When codesigning, use entitlements if available" ON)
 option(LLDB_BUILD_FRAMEWORK "Build LLDB.framework (Darwin only)" OFF)

>From 50fbbc56e37fca4514dd863b415c2a796cb5d32c Mon Sep 17 00:00:00 2001
From: Iasonaskrpr <iaskarapro at gmail.com>
Date: Mon, 6 Jul 2026 22:39:47 +0300
Subject: [PATCH 3/4] Added error message

---
 lldb/cmake/modules/LLDBConfig.cmake | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
index ffb01342531dc..23809b5c94f84 100644
--- a/lldb/cmake/modules/LLDBConfig.cmake
+++ b/lldb/cmake/modules/LLDBConfig.cmake
@@ -64,6 +64,15 @@ endif()
 
 option(LLDB_ENABLE_FORTRAN "Enable Fortran support in LLDB" ${LLDB_DEFAULT_ENABLE_FORTRAN})
 
+# Fail early if the user forced Fortran ON but we don't have in-tree Flang
+if(LLDB_ENABLE_FORTRAN AND NOT "flang" IN_LIST LLVM_ENABLE_PROJECTS)
+  message(FATAL_ERROR 
+    "Fortran support in LLDB requires an in-tree Flang build. "
+    "Please add 'flang' to LLVM_ENABLE_PROJECTS or disable Fortran "
+    "support by passing -DLLDB_ENABLE_FORTRAN=OFF."
+  )
+endif()
+
 add_optional_dependency(LLDB_ENABLE_SWIG "Enable SWIG to generate LLDB bindings" SWIG SWIG_FOUND VERSION 4)
 add_optional_dependency(LLDB_ENABLE_LIBEDIT "Enable editline support in LLDB" LibEdit LibEdit_FOUND)
 add_optional_dependency(LLDB_ENABLE_CURSES "Enable curses support in LLDB" CursesAndPanel CURSESANDPANEL_FOUND)

>From 9e620ae8a0e251001fdaf1fd4cfe82a318590d21 Mon Sep 17 00:00:00 2001
From: Iasonas Karaprodromidis <iaskarapro at gmail.com>
Date: Wed, 8 Jul 2026 15:53:34 +0300
Subject: [PATCH 4/4] Fix punctuation in comment

Co-authored-by: Jonas Devlieghere <jonas at devlieghere.com>
---
 lldb/cmake/modules/LLDBConfig.cmake | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/lldb/cmake/modules/LLDBConfig.cmake b/lldb/cmake/modules/LLDBConfig.cmake
index 23809b5c94f84..3f2e50cc7ab45 100644
--- a/lldb/cmake/modules/LLDBConfig.cmake
+++ b/lldb/cmake/modules/LLDBConfig.cmake
@@ -64,7 +64,7 @@ endif()
 
 option(LLDB_ENABLE_FORTRAN "Enable Fortran support in LLDB" ${LLDB_DEFAULT_ENABLE_FORTRAN})
 
-# Fail early if the user forced Fortran ON but we don't have in-tree Flang
+# Fail early if the user forced Fortran ON but we don't have in-tree Flang.
 if(LLDB_ENABLE_FORTRAN AND NOT "flang" IN_LIST LLVM_ENABLE_PROJECTS)
   message(FATAL_ERROR 
     "Fortran support in LLDB requires an in-tree Flang build. "

