[compiler-rt] [compiler-rt][GWP-ASan] Use no-op backtrace if execinfo.h missing (PR #201266)

[Brian Cain via llvm-commits]

https://github.com/androm3da created https://github.com/llvm/llvm-project/pull/201266

backtrace_linux_libc.cpp requires execinfo.h, which is not present in some C libraries (musl for example).

Add a cmake check_include_file guard: on targets with execinfo.h the existing RTGwpAsanBacktraceLibc is built unchanged; on targets without it a new RTGwpAsanBacktraceNone stub is built instead (all three function pointers return nullptr).  Mirror the same check in scudo/standalone so it links against whichever library was built.

>From 7d81f91ec3d9599511899cf775d2d5e0969dca81 Mon Sep 17 00:00:00 2001
From: Brian Cain <brian.cain at oss.qualcomm.com>
Date: Tue, 2 Jun 2026 19:50:25 -0500
Subject: [PATCH] [compiler-rt][GWP-ASan] Use no-op backtrace if execinfo.h
 missing

backtrace_linux_libc.cpp requires execinfo.h, which is not present in some
C libraries (musl for example).

Add a cmake check_include_file guard: on targets with execinfo.h the existing
RTGwpAsanBacktraceLibc is built unchanged; on targets without it a new
RTGwpAsanBacktraceNone stub is built instead (all three function pointers
return nullptr).  Mirror the same check in scudo/standalone so it links
against whichever library was built.
---
 compiler-rt/lib/gwp_asan/CMakeLists.txt       | 23 +++++++++++++++----
 .../lib/gwp_asan/optional/backtrace_none.cpp  | 22 ++++++++++++++++++
 .../lib/scudo/standalone/CMakeLists.txt       | 11 ++++++++-
 3 files changed, 50 insertions(+), 6 deletions(-)
 create mode 100644 compiler-rt/lib/gwp_asan/optional/backtrace_none.cpp

diff --git a/compiler-rt/lib/gwp_asan/CMakeLists.txt b/compiler-rt/lib/gwp_asan/CMakeLists.txt
index f638adda3abe1..6a7aaf19d05a1 100644
--- a/compiler-rt/lib/gwp_asan/CMakeLists.txt
+++ b/compiler-rt/lib/gwp_asan/CMakeLists.txt
@@ -90,11 +90,24 @@ add_compiler_rt_object_libraries(RTGwpAsanOptionsParser
     CFLAGS ${GWP_ASAN_OPTIONS_PARSER_CFLAGS})
 
 # As above, build the pre-implemented optional backtrace support libraries.
-add_compiler_rt_object_libraries(RTGwpAsanBacktraceLibc
-    ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
-    SOURCES optional/backtrace_linux_libc.cpp
-    ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
-    CFLAGS ${GWP_ASAN_CFLAGS})
+# backtrace_linux_libc.cpp requires execinfo.h.  On targets without it
+# build RTGwpAsanBacktraceNone which provides null stubs so that
+# GWP-ASan still functions as a guard allocator without stack-trace capture.
+include(CheckIncludeFile)
+check_include_file(execinfo.h COMPILER_RT_HAS_EXECINFO_H)
+if(COMPILER_RT_HAS_EXECINFO_H)
+  add_compiler_rt_object_libraries(RTGwpAsanBacktraceLibc
+      ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
+      SOURCES optional/backtrace_linux_libc.cpp
+      ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
+      CFLAGS ${GWP_ASAN_CFLAGS})
+else()
+  add_compiler_rt_object_libraries(RTGwpAsanBacktraceNone
+      ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
+      SOURCES optional/backtrace_none.cpp
+      ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
+      CFLAGS ${GWP_ASAN_CFLAGS})
+endif()
 add_compiler_rt_object_libraries(RTGwpAsanSegvHandler
     ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
     SOURCES optional/segv_handler_posix.cpp
diff --git a/compiler-rt/lib/gwp_asan/optional/backtrace_none.cpp b/compiler-rt/lib/gwp_asan/optional/backtrace_none.cpp
new file mode 100644
index 0000000000000..0530d2bb0c993
--- /dev/null
+++ b/compiler-rt/lib/gwp_asan/optional/backtrace_none.cpp
@@ -0,0 +1,22 @@
+//===-- backtrace_none.cpp --------------------------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+// Stub backtrace implementation for targets where execinfo.h is unavailable
+// (e.g. musl libc).  GWP-ASan still functions as a guard allocator; only
+// the stack-trace capture is absent.
+
+#include "gwp_asan/optional/backtrace.h"
+
+namespace gwp_asan {
+namespace backtrace {
+
+options::Backtrace_t getBacktraceFunction() { return nullptr; }
+PrintBacktrace_t getPrintBacktraceFunction() { return nullptr; }
+SegvBacktrace_t getSegvBacktraceFunction() { return nullptr; }
+
+} // namespace backtrace
+} // namespace gwp_asan
diff --git a/compiler-rt/lib/scudo/standalone/CMakeLists.txt b/compiler-rt/lib/scudo/standalone/CMakeLists.txt
index 20c59b4600613..1718f7e083f61 100644
--- a/compiler-rt/lib/scudo/standalone/CMakeLists.txt
+++ b/compiler-rt/lib/scudo/standalone/CMakeLists.txt
@@ -169,8 +169,17 @@ if (COMPILER_RT_HAS_GWP_ASAN)
   endif()
 
   add_dependencies(scudo_standalone gwp_asan)
+  # RTGwpAsanBacktraceLibc requires execinfo.h (not available on some C
+  # libs. Use RTGwpAsanBacktraceNone which provides null stubs.
+  include(CheckIncludeFile)
+  check_include_file(execinfo.h COMPILER_RT_HAS_EXECINFO_H)
+  if(COMPILER_RT_HAS_EXECINFO_H)
+    set(_gwp_asan_backtrace_lib RTGwpAsanBacktraceLibc)
+  else()
+    set(_gwp_asan_backtrace_lib RTGwpAsanBacktraceNone)
+  endif()
   list(APPEND SCUDO_OBJECT_LIBS
-       RTGwpAsan RTGwpAsanBacktraceLibc RTGwpAsanSegvHandler
+       RTGwpAsan ${_gwp_asan_backtrace_lib} RTGwpAsanSegvHandler
        RTGwpAsanOptionsParser)
 
   append_list_if(COMPILER_RT_HAS_OMIT_FRAME_POINTER_FLAG -fno-omit-frame-pointer