DCD crashes on startup in std.experimental.logger

[Hackerpilot]

Using LDC built from commit 6e0bada

Stack trace:

#0  0x0000000000598058 in rt.monitor_.ensureMonitor(Object) ()
#1  0x0000000000598126 in _d_monitorenter ()
#2  0x00000000004665e3 in std.experimental.logger.core.Logger.memLogFunctions!(64).logImpl!(160, "src/server/server.d", "server.server.main", "int server.server.main(string[] args)", "server.server", immutable(char)[], immutable(char)[]).logImpl(lazy immutable(char)[], lazy immutable(char)[]) (this=0x7ffff7fc38e8, _param_0={string delegate() (void)} 0x7fffffffd400, _param_1={string delegate() (void)} 0x7fffffffd3f0) at /usr/local/include/d/std/experimental/logger/core.d:948
#3  0x0000000000459178 in std.experimental.logger.core.defaultLogFunction!(64).defaultLogFunction!(160, "src/server/server.d", "server.server.main", "int server.server.main(string[] args)", "server.server", immutable(char)[], immutable(char)[]).defaultLogFunction(lazy immutable(char)[], lazy immutable(char)[]) (_param_0={string delegate() (void)} 0x7fffffffd468, _param_1={string delegate() (void)} 0x7fffffffd458) at /usr/local/include/d/std/experimental/logger/core.d:487
#4  0x000000000045723d in D main (args=...) at server.d:160

[Hackerpilot]

This may related to #1377.

[JohanEngelen]

@Hackerpilot Is it fixed by this?

--- a/gen/typinf.cpp
+++ b/gen/typinf.cpp
@@ -726,8 +726,11 @@ void TypeInfoDeclaration_codegen(TypeInfoDeclaration *decl, IRState *p) {
     } else {
       irg->type = LLStructType::create(gIR->context(), decl->toPrettyChars());
     }
-    LLGlobalVariable *g = new LLGlobalVariable(gIR->module, irg->type, true,
-                                               lwc.first, nullptr, mangled);
+    // Create the symbol. We need to keep it mutable as the type is not declared
+    // as immutable on the D side, plus synchronized() can be used on the
+    // implicit monitor.
+    auto g = new LLGlobalVariable(gIR->module, irg->type, false, lwc.first,
+                                  nullptr, mangled);
     setLinkage(lwc, g);
     irg->value = g;
   }

Thanks for testing!

[Hackerpilot]

It is. With that patch DCD passes its test suite.

[JohanEngelen]

@Hackerpilot Thanks for the fix confirmation.
Closing, as this is a duplicate of #1377.

[Hackerpilot]

I made a fresh clone of LDC master (fa8fe51), and tried this again and it's failing in the same place. I checked that CPP file and see that the fix is there, but the crash is back. Any ideas?

[JohanEngelen]

@Hackerpilot What happens when you apply the patch of this PR? #1384

[Hackerpilot]

That patch is against the ltsmaster branch, so I'll have to translate it to D first.

[JohanEngelen]

@Hackerpilot Sorry didn't notice, working on new PR here: #1385

[Hackerpilot]

For some reason that didn't break the build.

The line of ASM causing the segfault is

mov    rax,QWORD PTR [rax]

gdb tells me that the rax register's value at this point is 0.

Stack trace:

#0  0x00000000005a2a28 in rt.monitor_.ensureMonitor(Object) ()
#1  0x00000000005a2af6 in _d_monitorenter ()
#2  0x000000000046a793 in std.experimental.logger.core.Logger.memLogFunctions!(64).logImpl!(160, "src/server/server.d", "server.server.main", "int server.server.main(string[] args)", "server.server", immutable(char)[], immutable(char)[]).logImpl(lazy immutable(char)[], lazy immutable(char)[]) (this=0x7ffff7fc38e0, _param_0={string delegate() (void)} 0x7fffffffd410, _param_1={string delegate() (void)} 0x7fffffffd400) at /usr/local/include/d/std/experimental/logger/core.d:948
#3  0x000000000045d258 in std.experimental.logger.core.defaultLogFunction!(64).defaultLogFunction!(160, "src/server/server.d", "server.server.main", "int server.server.main(string[] args)", "server.server", immutable(char)[], immutable(char)[]).defaultLogFunction(lazy immutable(char)[], lazy immutable(char)[]) (_param_0={string delegate() (void)} 0x7fffffffd478, _param_1={string delegate() (void)} 0x7fffffffd468) at /usr/local/include/d/std/experimental/logger/core.d:487
#4  0x000000000045b33d in D main (args=...) at server.d:160

[JohanEngelen]

Could you dustmite it?
(the crash is exactly what I would expect from an optimization bug with synchronize on an immutable object)

[Hackerpilot]

I'm working on figuring out how to write the test script to catch that specific segfault.

Edit: https://github.com/CyberShadow/DustMite/wiki/Detecting-a-specific-segfault