[3.14] pythongh-137728 pythongh-137762: Fix bugs in the JIT with many local variables (pythonGH-137764) (python#137999)

Co-authored-by: Ken Jin <[email protected]>

Author: miss-islington

Misc/NEWS.d/next/Core_and_Builtins/2025-08-14-14-18-29.gh-issue-137728.HdYS9R.rst

@@ -0,0 +1 @@
+Fix the JIT's handling of many local variables. This previously caused a segfault.

Python/optimizer_analysis.c

@@ -449,13 +449,10 @@ optimize_uops(
     _Py_uop_abstractcontext_init(ctx);
     _Py_UOpsAbstractFrame *frame = _Py_uop_frame_new(ctx, co, curr_stacklen, NULL, 0);
     if (frame == NULL) {
-        return -1;
+        return 0;
     }
     ctx->curr_frame_depth++;
     ctx->frame = frame;
-    ctx->done = false;
-    ctx->out_of_space = false;
-    ctx->contradiction = false;
 
     _PyUOpInstruction *this_instr = NULL;
     for (int i = 0; !ctx->done; i++) {

Python/optimizer_symbols.c

@@ -691,6 +691,13 @@ _Py_uop_abstractcontext_init(JitOptContext *ctx)
 
     // Frame setup
     ctx->curr_frame_depth = 0;
+
+    // Ctx signals.
+    // Note: this must happen before frame_new, as it might override
+    // the result should frame_new set things to bottom.
+    ctx->done = false;
+    ctx->out_of_space = false;
+    ctx->contradiction = false;
 }
 
 int