C API: copying a PyStatus emits -Wdeprecated-declarations in C++ with clang since gh-158080 #160436

Bug description:

Since gh-158080 (GH-158085), PyStatus.exitcode is declared with Py_DEPRECATED(3.16) in Include/cpython/initconfig.h. Because the C API passes and returns PyStatus by value (PyStatus_Exception(), PyStatus_IsError(), Py_InitializeFromConfig(), ...), C++ code that uses the API in the documented way makes clang generate the implicit copy constructor / move assignment operator of PyStatus. These use the deprecated member, so clang emits -Wdeprecated-declarations even though the code never touches exitcode. With -Werror, the build fails.

The usage pattern of the Doc/c-api/init_config.rst examples (ex: init_python()), compiled as C++, is enough to reproduce:

#include <Python.h>

int main(int argc, char** argv) {
    PyStatus status;
    PyConfig config;
    PyConfig_InitPythonConfig(&config);
    status = PyConfig_SetBytesString(&config, &config.program_name, argv[0]);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    status = Py_InitializeFromConfig(&config);
    if (PyStatus_Exception(status)) {
        goto exception;
    }
    PyConfig_Clear(&config);
    return Py_RunMain();
exception:
    PyConfig_Clear(&config);
    Py_ExitStatusException(status);
}

$ clang++ -std=c++17 -Wall -Werror -I<cpython>/Include -I<build> -c embed.cpp
Include/cpython/initconfig.h:10:9: error: 'exitcode' is deprecated [-Werror,-Wdeprecated-declarations]
embed.cpp:7:12: note: in implicit move assignment operator for 'PyStatus' first required here
Include/cpython/initconfig.h:10:9: error: 'exitcode' is deprecated [-Werror,-Wdeprecated-declarations]
Include/cpython/initconfig.h:10:9: error: 'exitcode' is deprecated [-Werror,-Wdeprecated-declarations]
embed.cpp:8:28: note: in implicit copy constructor for 'PyStatus' first required here

• Reproduced with 3.16.0a1, with Ubuntu clang 21.1.8 (Linux aarch64) and Apple clang 21.0.0 (macOS arm64); the PyStatus definition is unchanged on current main.
• g++ 15, and clang compiling the same file as C, emit no warning.
• The diagnostic is reported at the definition of the structure in initconfig.h, so users cannot silence it locally with a pragma around their own calls; they have to wrap the #include <Python.h> itself.

Possible fix

Suppress the warning around the definition of the structure, with the existing _Py_COMP_DIAG_* macros of pyport.h:

 /* --- PyStatus ----------------------------------------------- */

+_Py_COMP_DIAG_PUSH
+_Py_COMP_DIAG_IGNORE_DEPR_DECLS
 typedef struct {
     enum {
         _PyStatus_TYPE_OK=0,
         _PyStatus_TYPE_ERROR=1,
         _PyStatus_TYPE_EXIT=2  // deprecated
     } _type;
     const char *func;
     const char *err_msg;
     Py_DEPRECATED(3.16) int exitcode;
 } PyStatus;
+_Py_COMP_DIAG_POP

With this change the example above compiles cleanly with clang++ -Werror, while real uses (status.exitcode, PyStatus_Exit(), PyStatus_IsExit()) still emit the deprecation warning. (Alternatively, only the functions could be marked deprecated and the member documented as deprecated.)

A C++ test in Lib/test/test_cppext that copies a PyStatus would catch regressions of this kind.

CPython versions tested on:

3.16, CPython main branch

Operating systems tested on:

Linux, macOS