Rust: Fix, increase worker thread stack size

[jmillan]

The mediasoup worker thread was spawned with the default stack size (macOS secondary thread stack size is ~2060 KB), causing a stack overflow when a WebRtcTransport with SCTP/DataChannels connected.

Association::AssertIsConsistent() calls MS_ASSERT 38 times. Each MS_ASSERT expands to MS_ABORT, which declares a local buffer:

char abortMessage[Logger::BufferSize];  // 50,000 bytes

38 × 50,000 = 1,900,000 bytes ≈ 1808 KB

This was confirmed by runtime probes and disassembly:

sub sp, sp, #0x1c3, lsl #12  ; 1,847,296 bytes
sub sp, sp, #0xf30           ;     3,888 bytes

When triggered from the WebRtcTransport DTLS path, which already has 334 KB of frames on the stack before reaching SCTP, the total exceeds the limit:

334 KB (DTLS base) + 1808 KB (AssertIsConsistent prologue) = 2142 KB
                                                            > 2060 KB → crash

Fix:

Spawn the worker thread with an explicit 8 MB stack via
std::thread::Builder::new().stack_size(8 * 1024 * 1024), giving
6062 KB of headroom at the deepest observed call site.

Also adds Utils::PrintThreadStack() / PrintStackTrace() — a stack-depth measurement utility used to diagnose this issue.

[ibc]

char abortMessage[Logger::BufferSize]; // 50,000 bytes

Perhaps this should be a thread static buffer?

Why isn't this a problem when using mediasoup with Node?

[jmillan]

Why isn't this a problem when using mediasoup with Node?

Because the stack size for the process is bigger.

[jmillan]

Perhaps this should be a thread static buffer?

Yes, we can do it thread static. I'm making it.

[ibc]

Perhaps this should be a thread static buffer?

Yes, we can do it thread static. I'm making it.

Wait wait, let's please check it carefully. For example, why aren't we using the already existing thread_local char Logger::buffer[Logger::BufferSize]? See Logger.cpp and Logger.hpp.

[jmillan]

Wait wait, let's please check it carefully. For example, why aren't we using the already existing thread_local char Logger::buffer[Logger::BufferSize]?

that's what I've done exactly. check last commit.

[ibc]

IMHO this is the only change we need:

diff --git a/worker/include/Logger.hpp b/worker/include/Logger.hpp
index 24092d64f..63f2fa810 100644
--- a/worker/include/Logger.hpp
+++ b/worker/include/Logger.hpp
@@ -470,11 +470,10 @@ public:
 #define MS_ABORT(desc, ...) \
 	do \
 	{ \
-		std::fprintf(stderr, "(ABORT) " _MS_LOG_STR_DESC desc _MS_LOG_SEPARATOR_CHAR_STD, _MS_LOG_ARG, ##__VA_ARGS__); \
+		std::snprintf(Logger::buffer, Logger::BufferSize, "(ABORT) " _MS_LOG_STR_DESC desc _MS_LOG_SEPARATOR_CHAR_STD, _MS_LOG_ARG, ##__VA_ARGS__); \
+		std::fprintf(stderr, "%s", Logger::buffer); \
 		std::fflush(stderr); \
-		char abortMessage[Logger::BufferSize]; \
-		std::snprintf(abortMessage, Logger::BufferSize, "(ABORT) " _MS_LOG_STR_DESC desc _MS_LOG_SEPARATOR_CHAR_STD, _MS_LOG_ARG, ##__VA_ARGS__); \
-		throw std::runtime_error(abortMessage); \
+		throw std::runtime_error(Logger::buffer); \
 	} \
 	while (false)
 #endif

[jmillan]

Changeing CHANGELOG's