Re: lib/60215: ld.elf_so dlerror() state is not thread-local

["Izumi Tsutsui via gnats" <gnats-admin%NetBSD.org@localhost>]

The following reply was made to PR lib/60215; it has been noted by GNATS.

From: Izumi Tsutsui <tsutsui%ceres.dti.ne.jp@localhost>
To: gnats-bugs%netbsd.org@localhost
Cc: tsutsui%ceres.dti.ne.jp@localhost
Subject: Re: lib/60215: ld.elf_so dlerror() state is not thread-local
Date: Wed, 29 Apr 2026 08:18:16 +0900

 > ld.elf_so doesn't itself have any notion of threads, which makes it 
 > quite hard to make error messages thread-safe.
 
 >From the application's point of view, this is not only about making
 error messages thread-safe.  If dlerror() state is process-global,
 the usual dlerror()/dlsym()/dlerror() sequence can report an
 unrelated error from another LWP and make the application take
 the wrong error path.
 
 For comparison, glibc does not use a single process-global dlerror
 state.  Its current implementation stores dlfcn failure state in
 thread-local storage:
 
 https://sourceware.org/git/?p=glibc.git;a=blob;f=dlfcn/dlerror.h;hb=66f3e9219d8f86b977d9be04ad469b5d72af0da2#l88
 
 ```
   86 /* Thread-local variable for storing dlfcn failures for subsequent
   87    reporting via dlerror.  */
   88 extern __thread struct dl_action_result *__libc_dlerror_result
   89   attribute_tls_model_ie;
 ```
 
 ---
 Izumi Tsutsui