From 232b51b3655d8a27764e2eb4a376f1a3014ac289 Mon Sep 17 00:00:00 2001
From: Tristan Stenner <ttstenner@gmail.com>
Date: Thu, 26 Nov 2020 11:01:13 +0100
Subject: [PATCH] Use per-thread error storage (thanks to @chkothe)

---
 src/common.cpp                  |  2 +-
 src/common.h                    |  2 +-
 testing/test_ext_streaminfo.cpp | 19 ++++++++++++++++++-
 3 files changed, 20 insertions(+), 3 deletions(-)

diff --git a/src/common.cpp b/src/common.cpp
index 67aa6ac82..f6385a280 100644
--- a/src/common.cpp
+++ b/src/common.cpp
@@ -11,7 +11,7 @@
 #include <mmsystem.h>
 #endif
 
-char last_error[512];
+thread_local char last_error[512] = {0};
 
 extern "C" {
 
diff --git a/src/common.h b/src/common.h
index 34fe8689b..4fc2ae11c 100644
--- a/src/common.h
+++ b/src/common.h
@@ -31,7 +31,7 @@ extern "C" {
 	"Please do not compile this with a lslboost version older than 1.45 because the library would otherwise not be protocol-compatible with builds using other versions."
 #endif
 
-extern char last_error[512];
+extern thread_local char last_error[512];
 
 // the highest supported protocol version
 // * 100 is the original version, supported by library versions 1.00+
diff --git a/testing/test_ext_streaminfo.cpp b/testing/test_ext_streaminfo.cpp
index 29e1fd0db..1319f64ba 100644
--- a/testing/test_ext_streaminfo.cpp
+++ b/testing/test_ext_streaminfo.cpp
@@ -1,10 +1,27 @@
 #include "catch.hpp"
 #include <lsl_cpp.h>
+#include <thread>
 
 namespace {
 
 TEST_CASE("streaminfo", "[streaminfo][basic]") {
 	CHECK_THROWS(lsl::stream_info("", "emptyname"));
-	CHECK(std::string("The name of a stream must be non-empty.") == lsl_last_error());
+	REQUIRE(std::string("The name of a stream must be non-empty.") == lsl_last_error());
+}
+
+TEST_CASE("multithreaded lsl_last_error", "[threading][basic]") {
+	CHECK_THROWS(lsl::stream_info("", "emptyname"));
+	std::thread([](){
+		CHECK_THROWS(lsl::stream_info("hasname","type", -1));
+		REQUIRE(std::string("The channel_count of a stream must be nonnegative.") == lsl_last_error());
+	}).join();
+	REQUIRE(std::string("The name of a stream must be non-empty.") == lsl_last_error());
+}
+
+/// Ensure that an overly long error message won't overflow the buffer
+TEST_CASE("lsl_last_error size", "[basic]") {
+	std::string invalidquery(512, '\'');
+	CHECK_THROWS(lsl::resolve_stream(invalidquery, 1, 0.1));
+	REQUIRE(lsl_last_error()[512] == 0);
 }
 } // namespace