[PATCH v2] Make GDB compile with Python 3 on MinGW

Christian Biesinger via gdb-patches
2019-08-14T16:06:26Z

[Now with the comment updated too]

PyFile_FromString and PyFile_AsFile have been removed in Python 3.
There is no obvious replacement that works here, and we can't just
pass our FILE* to a DLL in Windows because it may use a different
C runtime.

So we just call a Python function which reads and executes file
contents. Care must be taken to execute it in the context of
__main__.

Tested by inverting the ifdef and running the testsuite on Debian
Linux (even without the patch, I failed at running the testsuite
on Windows).

gdb/ChangeLog:

2019-08-13 Christian Biesinger <cbiesinger@google.com>

* python/lib/gdb/__init__.py: Add an execute_file function.
* python/python.c (python_run_simple_file): Call gdb.execute_file
on Windows.
---
gdb/python/lib/gdb/__init__.py | 23 +++++++++++++++++++++++
gdb/python/python.c | 23 +++++++++++++++--------
2 files changed, 38 insertions(+), 8 deletions(-)

diff --git a/gdb/python/lib/gdb/__init__.py b/gdb/python/lib/gdb/__init__.py
index af74df80c8..f1adc5ffbe 100644
--- a/gdb/python/lib/gdb/__init__.py
+++ b/gdb/python/lib/gdb/__init__.py
@@ -106,6 +106,29 @@ def execute_unwinders(pending_frame):

return None

+def execute_file(filepath):
+ """This function is used to replace Python 2's PyRun_SimpleFile.
+
+ Loads and executes the given file.
+
+ We could use the runpy module, but its documentation says:
+ "Furthermore, any functions and classes defined by the executed code are
+ not guaranteed to work correctly after a runpy function has returned."
+ """
+ globals = sys.modules['__main__'].__dict__
+ set_file = False
+ if not hasattr(globals, '__file__'):
+ globals['__file__'] = filepath
+ set_file = True
+ try:
+ with open(filepath, 'rb') as file:
+ # We pass globals also as locals to match what Python does
+ # in PyRun_SimpleFile.
+ exec(compile(file.read(), filepath, 'exec'), globals, globals)
+ finally:
+ if set_file:
+ del globals['__file__']
+

# Convenience variable to GDB's python directory
PYTHONDIR = os.path.dirname(os.path.dirname(__file__))
diff --git a/gdb/python/python.c b/gdb/python/python.c
index 162470dcc0..617bc0b84c 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -323,9 +323,8 @@ python_interactive_command (const char *arg, int from_tty)
A FILE * from one runtime does not necessarily operate correctly in
the other runtime.

- To work around this potential issue, we create on Windows hosts the
- FILE object using Python routines, thus making sure that it is
- compatible with the Python library. */
+ To work around this potential issue, we run code in Python to load
+ the script. */

static void
python_run_simple_file (FILE *file, const char *filename)
@@ -339,14 +338,22 @@ python_run_simple_file (FILE *file, const char *filename)
/* Because we have a string for a filename, and are using Python to
open the file, we need to expand any tilde in the path first. */
gdb::unique_xmalloc_ptr<char> full_path (tilde_expand (filename));
- gdbpy_ref<> python_file (PyFile_FromString (full_path.get (), (char *) "r"));
- if (python_file == NULL)
+
+ if (gdb_python_module == nullptr
+ || ! PyObject_HasAttrString (gdb_python_module, "execute_file"))
{
- gdbpy_print_stack ();
- error (_("Error while opening file: %s"), full_path.get ());
+ error (_("Installation error: gdb.execute_file function is missing"));
+ return;
}

- PyRun_SimpleFile (PyFile_AsFile (python_file.get ()), filename);
+ gdbpy_ref<> return_value
+ (PyObject_CallMethod (gdb_python_module, "execute_file", "s", full_path.get ()));
+ if (return_value == nullptr)
+ {
+ /* Use PyErr_PrintEx instead of gdbpy_print_stack to better match the
+ behavior of the non-Windows codepath. */
+ PyErr_PrintEx(0);
+ }

#endif /* _WIN32 */
}
--
2.23.0.rc1.153.gdeed80330f-goog