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bpo-38634: Allow non-apple build to cope with libedit #16986

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Dec 4, 2019
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bpo-38634: Allow non-apple build to cope with libedit #16986

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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Library/2019-12-04-15-56-28.bpo-38634.pq0ZWa.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
The :mod:`readline` module now detects if Python is linked to libedit at runtime
on all platforms. Previously, the check was only done on macOS.
23 changes: 4 additions & 19 deletions Modules/readline.c
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Original file line number Diff line number Diff line change
Expand Up @@ -45,14 +45,14 @@ extern char **completion_matches(char *, CPFunction *);
#endif
#endif

#ifdef __APPLE__
/*
* It is possible to link the readline module to the readline
* emulation library of editline/libedit.
*
* On OSX this emulation library is not 100% API compatible
* with the "real" readline and cannot be detected at compile-time,
* hence we use a runtime check to detect if we're using libedit
* This emulation library is not 100% API compatible with the "real" readline
* and cannot be detected at compile-time,
* hence we use a runtime check to detect if the Python readlinke module is
* linked to libedit.
*
* Currently there is one known API incompatibility:
* - 'get_history' has a 1-based index with GNU readline, and a 0-based
Expand All @@ -64,7 +64,6 @@ static int using_libedit_emulation = 0;
static const char libedit_version_tag[] = "EditLine wrapper";

static int libedit_history_start = 0;
#endif /* __APPLE__ */

#ifdef HAVE_RL_COMPLETION_DISPLAY_MATCHES_HOOK
static void
Expand Down Expand Up @@ -693,7 +692,6 @@ get_history_item(PyObject *self, PyObject *args)

if (!PyArg_ParseTuple(args, "i:get_history_item", &idx))
return NULL;
#ifdef __APPLE__
if (using_libedit_emulation) {
/* Older versions of libedit's readline emulation
* use 0-based indexes, while readline and newer
Expand All @@ -713,7 +711,6 @@ get_history_item(PyObject *self, PyObject *args)
Py_RETURN_NONE;
}
}
#endif /* __APPLE__ */
if ((hist_ent = history_get(idx)))
return decode(hist_ent->line);
else {
Expand Down Expand Up @@ -1080,7 +1077,6 @@ setup_readline(readlinestate *mod_state)
/* The name must be defined before initialization */
rl_readline_name = "python";

#ifdef __APPLE__
/* the libedit readline emulation resets key bindings etc
* when calling rl_initialize. So call it upfront
*/
Expand All @@ -1097,7 +1093,6 @@ setup_readline(readlinestate *mod_state)
libedit_history_start = 1;
}
clear_history();
#endif /* __APPLE__ */

using_history();

Expand Down Expand Up @@ -1126,9 +1121,7 @@ setup_readline(readlinestate *mod_state)
mod_state->begidx = PyLong_FromLong(0L);
mod_state->endidx = PyLong_FromLong(0L);

#ifdef __APPLE__
if (!using_libedit_emulation)
#endif
{
if (!isatty(STDOUT_FILENO)) {
/* Issue #19884: stdout is not a terminal. Disable meta modifier
Expand All @@ -1148,11 +1141,9 @@ setup_readline(readlinestate *mod_state)
* XXX: A bug in the readline-2.2 library causes a memory leak
* inside this function. Nothing we can do about it.
*/
#ifdef __APPLE__
if (using_libedit_emulation)
rl_read_init_file(NULL);
else
#endif /* __APPLE__ */
rl_initialize();

RESTORE_LOCALE(saved_locale)
Expand Down Expand Up @@ -1281,12 +1272,10 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
int length = _py_get_history_length();
if (length > 0) {
HIST_ENTRY *hist_ent;
#ifdef __APPLE__
if (using_libedit_emulation) {
/* handle older 0-based or newer 1-based indexing */
hist_ent = history_get(length + libedit_history_start - 1);
} else
#endif /* __APPLE__ */
hist_ent = history_get(length);
line = hist_ent ? hist_ent->line : "";
} else
Expand Down Expand Up @@ -1314,10 +1303,8 @@ call_readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
PyDoc_STRVAR(doc_module,
"Importing this module enables command line editing using GNU readline.");

#ifdef __APPLE__
PyDoc_STRVAR(doc_module_le,
"Importing this module enables command line editing using libedit readline.");
#endif /* __APPLE__ */

static struct PyModuleDef readlinemodule = {
PyModuleDef_HEAD_INIT,
Expand All @@ -1338,15 +1325,13 @@ PyInit_readline(void)
PyObject *m;
readlinestate *mod_state;

#ifdef __APPLE__
if (strncmp(rl_library_version, libedit_version_tag, strlen(libedit_version_tag)) == 0) {
using_libedit_emulation = 1;
}

if (using_libedit_emulation)
readlinemodule.m_doc = doc_module_le;

#endif /* __APPLE__ */

m = PyModule_Create(&readlinemodule);

Expand Down