`traverse_module_state` can return `int`, do not use `(void)` for it · Issue #135839 · python/cpython · GitHub

Bug report

traverse_module_state can in theory return non-zero code:

Lines 283 to 302 in 0d9d489

    
           static int 
        
           traverse_module_state(module_state *state, visitproc visit, void *arg) 
        
           { 
        
               /* external types */ 
        
               Py_VISIT(state->send_channel_type); 
        
               Py_VISIT(state->recv_channel_type); 
        
               /* heap types */ 
        
               Py_VISIT(state->ChannelInfoType); 
        
               Py_VISIT(state->ChannelIDType); 
        
               /* exceptions */ 
        
               Py_VISIT(state->ChannelError); 
        
               Py_VISIT(state->ChannelNotFoundError); 
        
               Py_VISIT(state->ChannelClosedError); 
        
               Py_VISIT(state->ChannelEmptyError); 
        
               Py_VISIT(state->ChannelNotEmptyError); 
        
               return 0; 
        
           }

because PY_VISIT can return it:

cpython/Include/objimpl.h

Lines 193 to 200 in 0d9d489

    
           #define Py_VISIT(op)                                                    \ 
        
               do {                                                                \ 
        
                   if (op) {                                                       \ 
        
                       int vret = visit(_PyObject_CAST(op), arg);                  \ 
        
                       if (vret)                                                   \ 
        
                           return vret;                                            \ 
        
                   }                                                               \ 
        
               } while (0)

So, using it like this:

cpython/Modules/_interpchannelsmodule.c

Lines 3627 to 3629 in 0d9d489

    
           // Now we clear the module state. 
        
           (void)clear_module_state(state); 
        
           return 0;

Is also not really correct. I will send a PR with the fix.

Linked PRs

pythongh-135839: Fix `traverse_module_state` usage in `_interpchannel…

FWIW, I peaked at the git blame, and I didn't find any discussions in the past PRs about wanting to ignore the return value

gh-135839: Fix `module_traverse` and `module_clear` in `_interpchanne…

pythongh-135839: Fix `module_traverse` and `module_clear` in `_interp…

[3.13] pythongh-135839: Fix `module_traverse` and `module_clear` in `…

The same happens in Modules/_interpretersmodule.c, I will check for other usages and create one more PR with the fix of other cases.

[3.14] gh-135839: Fix `module_traverse` and `module_clear` in `_inter…

[3.13] gh-135839: Fix `module_traverse` and `module_clear` in `_inter…

gh-135839: Fix `module_traverse` and `module_clear` in subinterp modu…

pythongh-135839: Fix `module_traverse` and `module_clear` in subinter…

[3.14] gh-135839: Fix `module_traverse` and `module_clear` in subinte…

[3.13] pythongh-135839: Fix `module_traverse` and `module_clear` in s…

pythongh-135839: Fix `module_traverse` and `module_clear` in `_interp…

pythongh-135839: Fix `module_traverse` and `module_clear` in subinter…

pythongh-135839: Fix `module_traverse` and `module_clear` in `_interp…

pythongh-135839: Fix `module_traverse` and `module_clear` in subinter…

[3.13] gh-135839: Fix `module_traverse` and `module_clear` in subinte…

pythongh-135839: Fix `module_traverse` and `module_clear` in `_interp…

pythongh-135839: Fix `module_traverse` and `module_clear` in subinter…

pythongh-135839: Fix `module_traverse` and `module_clear` in `_interp…

pythongh-135839: Fix `module_traverse` and `module_clear` in subinter…

`traverse_module_state` can return `int`, do not use `(void)` for it · Issue #135839 · python/cpython · GitHub

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traverse_module_state can return int, do not use (void) for it #135839

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	static int
	traverse_module_state(module_state state, visitproc visit, void arg)
	{
	/* external types */
	Py_VISIT(state->send_channel_type);
	Py_VISIT(state->recv_channel_type);

	/* heap types */
	Py_VISIT(state->ChannelInfoType);
	Py_VISIT(state->ChannelIDType);

	/* exceptions */
	Py_VISIT(state->ChannelError);
	Py_VISIT(state->ChannelNotFoundError);
	Py_VISIT(state->ChannelClosedError);
	Py_VISIT(state->ChannelEmptyError);
	Py_VISIT(state->ChannelNotEmptyError);

	return 0;
	}

	#define Py_VISIT(op) \
	do { \
	if (op) { \
	int vret = visit(_PyObject_CAST(op), arg); \
	if (vret) \
	return vret; \
	} \
	} while (0)

	// Now we clear the module state.
	(void)clear_module_state(state);
	return 0;

`traverse_module_state` can return `int`, do not use `(void)` for it · Issue #135839 · python/cpython · GitHub

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traverse_module_state can return int, do not use (void) for it #135839

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brianschubert commented on Jun 23, 2025

sobolevn commented on Jun 25, 2025

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