kit

commit d59a75252c48f351272b3e61368818584582118b
parent f8164e2795d7e8f74d270efd23968f1dace98db8
Author: Ryan Sepassi <rsepassi@gmail.com>
Date:   Tue,  9 Jun 2026 12:15:42 -0700

cg: report non-local-exec TLS models as unsupported

kit_cg_target_supports_symbol_feature reported initial-exec / local-dynamic
/ general-dynamic as supported on any TLS-capable format (ELF/Mach-O), but
kit emits local-exec only -- so a caller could request a dynamic model and
silently receive local-exec.

Report the truth: local-exec stays format-gated; the three dynamic models
return 0 (no codegen, no __tls_get_addr runtime). The linker enforces the
same contract at link time (link_require_local_tls).

obj_format_supports_symbol_feature is left unchanged: its contract is format
representability (ELF can represent IE relocs), which stays honest; it is now
only consulted for local-exec.

Extend 64_target_feature_queries.toy to assert the three dynamic models
report false on every target.

Diffstat:
M
src/cg/type.c
 | 
11
++++++++++-
M
test/toy/cases/64_target_feature_queries.toy
 | 
10
+++++++++-

2 files changed, 19 insertions(+), 2 deletions(-)
diff --git a/src/cg/type.c b/src/cg/type.c
@@ -916,10 +916,19 @@ int kit_cg_target_supports_symbol_feature(KitCompiler* c,
     case KIT_CG_SYMFEAT_COMMON:
       return 1;
     case KIT_CG_SYMFEAT_TLS_LOCAL_EXEC:
+      /* Local-exec is the only TLS model kit emits.  Whether it is actually
+       * available still depends on the object format being able to represent a
+       * TLS access at all (ELF/Mach-O yes; COFF/Wasm no). */
+      return obj_format_supports_symbol_feature(c, (int)feat);
     case KIT_CG_SYMFEAT_TLS_INITIAL_EXEC:
     case KIT_CG_SYMFEAT_TLS_LOCAL_DYNAMIC:
     case KIT_CG_SYMFEAT_TLS_GENERAL_DYNAMIC:
-      return obj_format_supports_symbol_feature(c, (int)feat);
+      /* kit has no initial-exec / local-dynamic / general-dynamic codegen and
+       * no dynamic-TLS runtime (__tls_get_addr), so it never emits these even
+       * where the object format could represent them.  Report the truth so a
+       * caller can't request a dynamic model and silently get local-exec; the
+       * linker enforces the same contract (see link_require_local_tls). */
+      return 0;
     case KIT_CG_SYMFEAT_DLLIMPORT:
     case KIT_CG_SYMFEAT_DLLEXPORT:
     case KIT_CG_SYMFEAT_MERGE_SECTIONS:
diff --git a/test/toy/cases/64_target_feature_queries.toy b/test/toy/cases/64_target_feature_queries.toy
@@ -3,8 +3,16 @@ fn __user_main(): i64 {
   let common_ok: bool = @supports_symbol_feature(.common);
   let strict: bool = @has_backend_feature(.strict_alignment);
   let red_zone: bool = @has_backend_feature(.red_zone);
+  // kit emits local-exec TLS only.  The capability query must be honest about
+  // that on every target: initial-exec / local-dynamic / general-dynamic are
+  // never emitted, so they must never report as supported (regardless of
+  // whether the object format could otherwise represent them).
+  let ie: bool = @supports_symbol_feature(.tls_initial_exec);
+  let ld: bool = @supports_symbol_feature(.tls_local_dynamic);
+  let gd: bool = @supports_symbol_feature(.tls_general_dynamic);
   if (weak_ok or !weak_ok) and (common_ok or !common_ok) and
-     (strict or !strict) and (red_zone or !red_zone) {
+     (strict or !strict) and (red_zone or !red_zone) and
+     !ie and !ld and !gd {
     return 42;
   }
   return 1;