gh-125207: Fix MSVC 1935 build with JIT (#125209)

* gh-125207: Use {0} array initializers

* Simplify, as suggested in PR

* Revert change to explicitly specify length

Signed-off-by: Pablo Galindo <[email protected]>

Author: mdboom

Python/ceval.c

@@ -99,6 +99,11 @@
         } \
         _Py_DECREF_STAT_INC(); \
         if (--op->ob_refcnt == 0) { \
+            struct _reftracer_runtime_state *tracer = &_PyRuntime.ref_tracer; \
+            if (tracer->tracer_func != NULL) { \
+                void* data = tracer->tracer_data; \
+                tracer->tracer_func(op, PyRefTracer_DESTROY, data); \
+            } \
             destructor d = (destructor)(dealloc); \
             d(op); \
         } \

Python/jit.c

@@ -469,7 +469,7 @@ _PyJIT_Compile(_PyExecutorObject *executor, const _PyUOpInstruction trace[], siz
     // Loop once to find the total compiled size:
     size_t code_size = 0;
     size_t data_size = 0;
-    jit_state state = {};
+    jit_state state = {0};
     group = &trampoline;
     code_size += group->code_size;
     data_size += group->data_size;

Tools/jit/_writer.py

@@ -32,8 +32,11 @@ def _dump_footer(
     yield "};"
     yield ""
     yield f"static const void * const symbols_map[{max(len(symbols), 1)}] = {{"
-    for symbol, ordinal in symbols.items():
-        yield f"    [{ordinal}] = &{symbol},"
+    if symbols:
+        for symbol, ordinal in symbols.items():
+            yield f"    [{ordinal}] = &{symbol},"
+    else:
+        yield "    0"
     yield "};"