`malloc(): unaligned tcache chunk detected` from `roc-htmx-playground` using `basic-webserver`

[gree7]

When testing https://github.com/lukewilliamboswell/roc-htmx-playground (which uses basic-web), the variant working with the current Roc is in lukewilliamboswell/roc-htmx-playground#9, I hit this error:

$ DB_PATH=test.db roc run --linker=legacy src/main.roc
Listening on <http://127.0.0.1:8000>
2024-11-27T11:24:25Z Get /
2024-11-27T11:24:25Z Get /bootstrap.min.css
2024-11-27T11:24:25Z Get /styles.css
2024-11-27T11:24:25Z Get /bootstrap.bundle.min.js
2024-11-27T11:24:25Z Get /htmx.min.js
2024-11-27T11:24:25Z Get /site.js
2024-11-27T11:24:27Z Get /treeview
2024-11-27T11:24:27Z Get /bigTask
2024-11-27T11:24:29Z Get /bigTask?page=2&items=25
2024-11-27T11:24:31Z Get /bigTask?page=3&items=25
2024-11-27T11:24:33Z Get /bigTask?page=4&items=25
2024-11-27T11:24:34Z Get /bigTask?page=2&items=25
malloc(): unaligned tcache chunk detected

I saw the error only at the /bigTask?... requests and the error is happening randomly, but at least on my machine always until 5th request on the /bigTask?....

The run with Valgrind looked like this:

$ DB_PATH=test.db valgrind src/main
==3385473== Memcheck, a memory error detector
==3385473== Copyright (C) 2002-2024, and GNU GPL'd, by Julian Seward et al.
==3385473== Using Valgrind-3.24.0 and LibVEX; rerun with -h for copyright info
==3385473== Command: src/main
==3385473==
==3385473== posix_memalign() invalid size value: 0
==3385473==    at 0x484CA38: posix_memalign (vg_replace_malloc.c:2226)
==3385473==    by 0x273990: rust_main (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x48D5E07: (below main) (libc_start_call_main.h:58)
==3385473==
Listening on <http://127.0.0.1:8000>
2024-11-28T09:40:05Z Get /
2024-11-28T09:40:06Z Get /bootstrap.min.css
2024-11-28T09:40:06Z Get /bootstrap.bundle.min.js
2024-11-28T09:40:06Z Get /styles.css
2024-11-28T09:40:06Z Get /htmx.min.js
2024-11-28T09:40:06Z Get /site.js
2024-11-28T09:40:06Z Get /favicon.ico
404 NotFound /favicon.ico
2024-11-28T09:40:07Z Get /bigTask
2024-11-28T09:40:10Z Get /bigTask?page=2&items=25
==3385473== Thread 20 tokio-runtime-w:
==3385473== Invalid read of size 8
==3385473==    at 0x222789: decrement_refcounted_ptr_8 (roc_app:0)
==3385473==    by 0x22277D: ??? (roc_app:0)
==3385473==    by 0x229287: ??? (roc_app:0)
==3385473==    by 0x1C0D18: Task_53_b7f067e6f5939fbe06dd68ed4b36fad898cbfd8ef8d993964d5cd10b12ac3ec (roc_app:0)
==3385473==    by 0x1ECAD1: Task_96_38ac12d038fd8df52070eb8edb3aab96b2fa7b50fc7a9367255428634fa0264e (roc_app:0)
==3385473==    by 0x218289: Task_46_5e6d2773e4caec97557de41edef7addcc8c8bc472f779d224a7d61166dbaabe (roc_app:0)
==3385473==    by 0x1E7D02: _158_3fe74881edf546beefa6734056b1899c37505b1c34fcce49bbd7b44b157595 (roc_app:0)
==3385473==    by 0x22C6CD: roc__forHost_2_caller (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x29A7ED: tokio::runtime::task::raw::poll (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E762D: std::sys_common::backtrace::__rust_begin_short_backtrace (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E736E: core::ops::function::FnOnce::call_once{{vtable.shim}} (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E3ADA: call_once<(), dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: call_once<(), alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: std::sys::pal::unix::thread::Thread::new::thread_start (thread.rs:108)
==3385473==  Address 0x77720a0 is 0 bytes inside a block of size 32 free'd
==3385473==    at 0x48478EF: free (vg_replace_malloc.c:989)
==3385473==    by 0x2227CA: decrement_refcounted_ptr_8 (roc_app:0)
==3385473==    by 0x22277D: ??? (roc_app:0)
==3385473==    by 0x1A20BA: Controllers.BigTask_15_36cf1b423d96d0d1f556ed298e83394497cd597c20b08eba5512c2685cd67751 (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x1C46BD: Task_46_c436285c5b59d7df49ab96ad8476bdb7c10421fe2225ff48721cb48682ff451 (roc_app:0)
==3385473==    by 0x1CCDFE: Task_46_28ea24f1682fb667c3fb23a9dbc02f29e624f88b5aca38a345144704a3139a (roc_app:0)
==3385473==    by 0x1FF9B2: Task_46_ee6d8d949dc3617ea48fd44bd0c8f21be51d3676b1b3bdfdfcf8f559e4e0272f (roc_app:0)
==3385473==    by 0x222172: Task_46_1f3cd98ac177094c9632f9c81aa71556d2feacfd911d3d139427ec94325c8 (roc_app:0)
==3385473==    by 0x1C0D04: Task_53_b7f067e6f5939fbe06dd68ed4b36fad898cbfd8ef8d993964d5cd10b12ac3ec (roc_app:0)
==3385473==    by 0x1ECAD1: Task_96_38ac12d038fd8df52070eb8edb3aab96b2fa7b50fc7a9367255428634fa0264e (roc_app:0)
==3385473==    by 0x218289: Task_46_5e6d2773e4caec97557de41edef7addcc8c8bc472f779d224a7d61166dbaabe (roc_app:0)
==3385473==    by 0x1E7D02: _158_3fe74881edf546beefa6734056b1899c37505b1c34fcce49bbd7b44b157595 (roc_app:0)
==3385473==  Block was alloc'd at
==3385473==    at 0x48447A8: malloc (vg_replace_malloc.c:446)
==3385473==    by 0x2B074D: <roc_std::roc_str::RocStr as core::convert::From<&str>>::from (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x29A5CA: tokio::runtime::task::raw::poll (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E762D: std::sys_common::backtrace::__rust_begin_short_backtrace (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E736E: core::ops::function::FnOnce::call_once{{vtable.shim}} (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E3ADA: call_once<(), dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: call_once<(), alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: std::sys::pal::unix::thread::Thread::new::thread_start (thread.rs:108)
==3385473==    by 0x494439C: start_thread (pthread_create.c:447)
==3385473==    by 0x49C92A3: clone (clone.S:100)
==3385473==
==3385473== Invalid write of size 8
==3385473==    at 0x2227AA: decrement_refcounted_ptr_8 (roc_app:0)
==3385473==    by 0x22277D: ??? (roc_app:0)
==3385473==    by 0x229287: ??? (roc_app:0)
==3385473==    by 0x1C0D18: Task_53_b7f067e6f5939fbe06dd68ed4b36fad898cbfd8ef8d993964d5cd10b12ac3ec (roc_app:0)
==3385473==    by 0x1ECAD1: Task_96_38ac12d038fd8df52070eb8edb3aab96b2fa7b50fc7a9367255428634fa0264e (roc_app:0)
==3385473==    by 0x218289: Task_46_5e6d2773e4caec97557de41edef7addcc8c8bc472f779d224a7d61166dbaabe (roc_app:0)
==3385473==    by 0x1E7D02: _158_3fe74881edf546beefa6734056b1899c37505b1c34fcce49bbd7b44b157595 (roc_app:0)
==3385473==    by 0x22C6CD: roc__forHost_2_caller (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x29A7ED: tokio::runtime::task::raw::poll (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E762D: std::sys_common::backtrace::__rust_begin_short_backtrace (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E736E: core::ops::function::FnOnce::call_once{{vtable.shim}} (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E3ADA: call_once<(), dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: call_once<(), alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: std::sys::pal::unix::thread::Thread::new::thread_start (thread.rs:108)
==3385473==  Address 0x77720a0 is 0 bytes inside a block of size 32 free'd
==3385473==    at 0x48478EF: free (vg_replace_malloc.c:989)
==3385473==    by 0x2227CA: decrement_refcounted_ptr_8 (roc_app:0)
==3385473==    by 0x22277D: ??? (roc_app:0)
==3385473==    by 0x1A20BA: Controllers.BigTask_15_36cf1b423d96d0d1f556ed298e83394497cd597c20b08eba5512c2685cd67751 (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x1C46BD: Task_46_c436285c5b59d7df49ab96ad8476bdb7c10421fe2225ff48721cb48682ff451 (roc_app:0)
==3385473==    by 0x1CCDFE: Task_46_28ea24f1682fb667c3fb23a9dbc02f29e624f88b5aca38a345144704a3139a (roc_app:0)
==3385473==    by 0x1FF9B2: Task_46_ee6d8d949dc3617ea48fd44bd0c8f21be51d3676b1b3bdfdfcf8f559e4e0272f (roc_app:0)
==3385473==    by 0x222172: Task_46_1f3cd98ac177094c9632f9c81aa71556d2feacfd911d3d139427ec94325c8 (roc_app:0)
==3385473==    by 0x1C0D04: Task_53_b7f067e6f5939fbe06dd68ed4b36fad898cbfd8ef8d993964d5cd10b12ac3ec (roc_app:0)
==3385473==    by 0x1ECAD1: Task_96_38ac12d038fd8df52070eb8edb3aab96b2fa7b50fc7a9367255428634fa0264e (roc_app:0)
==3385473==    by 0x218289: Task_46_5e6d2773e4caec97557de41edef7addcc8c8bc472f779d224a7d61166dbaabe (roc_app:0)
==3385473==    by 0x1E7D02: _158_3fe74881edf546beefa6734056b1899c37505b1c34fcce49bbd7b44b157595 (roc_app:0)
==3385473==  Block was alloc'd at
==3385473==    at 0x48447A8: malloc (vg_replace_malloc.c:446)
==3385473==    by 0x2B074D: <roc_std::roc_str::RocStr as core::convert::From<&str>>::from (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x29A5CA: tokio::runtime::task::raw::poll (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E762D: std::sys_common::backtrace::__rust_begin_short_backtrace (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E736E: core::ops::function::FnOnce::call_once{{vtable.shim}} (in /home/gree/workspace/roc-htmx-playground/src/main)
==3385473==    by 0x2E3ADA: call_once<(), dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: call_once<(), alloc::boxed::Box<dyn core::ops::function::FnOnce<(), Output=()>, alloc::alloc::Global>, alloc::alloc::Global> (boxed.rs:2022)
==3385473==    by 0x2E3ADA: std::sys::pal::unix::thread::Thread::new::thread_start (thread.rs:108)
==3385473==    by 0x494439C: start_thread (pthread_create.c:447)
==3385473==    by 0x49C92A3: clone (clone.S:100)
==3385473==

The related Zulip discussion with hypotheses what the problem could be is here: https://roc.zulipchat.com/#narrow/channel/231634-beginners/topic/client-side.20web.20in.20Roc/near/484698508

[Anton-4]

In case it may help anyone, we've have had a malloc(): unaligned tcache chunk detected before with the static site gen platform roc-lang/roc#5430

[Anton-4]

Some comments from Brendan:

Yeah, this suggests that we are allocating something with the wrong size. Allocate something with no size, attempt to read a refcount from it (invalid read cause didn't allocate space for a recount), attempt to write refcount to it (invalid write).

My first guess is allocating a Box {} is not adding on the refcount.

In roc-lang/roc#5430 we also had a problem with box