From d2079574c7fe1d47b4b33434a33bb6510a97202a Mon Sep 17 00:00:00 2001
From: Pratik Mankawde <3397372+pratikmankawde@users.noreply.github.com>
Date: Thu, 19 Mar 2026 11:18:14 +0000
Subject: [PATCH] fix: Build Boost.Context with ucontext backend for TSAN
 builds

TSAN cannot instrument fcontext (assembly) context switches, causing
undefined symbol errors for fiber_activation_record::current(). Add
Conan build options and CMake defines to use the ucontext backend
for TSAN, matching the existing ASAN configuration.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 cmake/deps/Boost.cmake    | 11 +++++++++++
 conan/profiles/sanitizers |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/cmake/deps/Boost.cmake b/cmake/deps/Boost.cmake
index 7594ddc806..3b4e165dcf 100644
--- a/cmake/deps/Boost.cmake
+++ b/cmake/deps/Boost.cmake
@@ -61,3 +61,14 @@ if(enable_asan)
         INTERFACE BOOST_USE_ASAN BOOST_USE_UCONTEXT
     )
 endif()
+
+# TSAN also requires the ucontext backend so that Boost.Context uses
+# POSIX ucontext (not fcontext assembly) for fiber switching. This
+# allows TSAN to properly track context switches and avoids false positives.
+# These defines must match what Boost was compiled with (see conan/profiles/sanitizers).
+if(enable_tsan)
+    target_compile_definitions(
+        xrpl_boost
+        INTERFACE BOOST_USE_TSAN BOOST_USE_UCONTEXT
+    )
+endif()
diff --git a/conan/profiles/sanitizers b/conan/profiles/sanitizers
index 6d37425f43..6af5565bcb 100644
--- a/conan/profiles/sanitizers
+++ b/conan/profiles/sanitizers
@@ -82,5 +82,12 @@ tools.info.package_id:confs+=["tools.build:cxxflags", "tools.build:exelinkflags"
         boost/*:without_context=False
         # Boost stacktrace fails to build with some sanitizers
         boost/*:without_stacktrace=True
+    {% elif "thread" in sanitizers %}
+        # Build Boost.Context with ucontext backend (not fcontext) so that
+        # TSAN can instrument fiber/context switches. fcontext uses raw assembly
+        # which TSAN cannot intercept, causing false positives and link errors.
+        boost/*:extra_b2_flags=context-impl=ucontext thread-sanitizer=on define=BOOST_USE_TSAN=1
+        boost/*:without_context=False
+        boost/*:without_stacktrace=True
     {% endif %}
 {% endif %}