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gh-151112: Fix crash in compiler_mod() when entering the current compilation unit fails #151234

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gh-151112: Fix crash in compiler_mod() when entering the current compilation unit fails #151234

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6c856bc
Fix crash in `compiler_mod()` when entering the current compilation u…
StanFromIreland Jun 10, 2026
9f0e7d6
Add assert for c->u being NULL
StanFromIreland Jun 10, 2026
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5 changes: 4 additions & 1 deletion Python/compile.c
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Original file line number Diff line number Diff line change
Expand Up @@ -893,12 +893,15 @@ compiler_mod(compiler *c, mod_ty mod)
{
PyCodeObject *co = NULL;
int addNone = mod->kind != Expression_kind;
assert(c->u == NULL);
if (compiler_codegen(c, mod) < 0) {
goto finally;
}
co = _PyCompile_OptimizeAndAssemble(c, addNone);
finally:
_PyCompile_ExitScope(c);
if (c->u != NULL) {

@iritkatriel iritkatriel Jun 10, 2026

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Are we sure c->u was NULL when we entered compiler_mod? Can we assert that at the top of the function?

@StanFromIreland StanFromIreland Jun 10, 2026

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Yes, in _PyAST_Compile we initialise c:

cpython/Python/compile.c

Lines 1527 to 1532 in 9fd1a12

compiler *c = new_compiler(mod, filename, pflags, optimize, arena, module);
if (c == NULL) {
return NULL;
}
PyCodeObject *co = compiler_mod(c, mod);

But new_compiler doesn't set c->u.

_PyCompile_ExitScope(c);
}
return co;
}

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