`pymain_run_file_obj`: validate file type before reading

[nybblista]

pymain_run_file_obj attempts to skip the source first line before verifying that the file is not a directory.

cpython/Modules/main.c

Lines 382 to 401 in 4eab90f

	if (skip_source_first_line) {
	int ch;
	/* Push back first newline so line numbers remain the same */
	while ((ch = getc(fp)) != EOF) {
	if (ch == '\n') {
	(void)ungetc(ch, fp);
	break;
	}
	}
	}
	struct _Py_stat_struct sb;
	if (_Py_fstat_noraise(fileno(fp), &sb) == 0 && S_ISDIR(sb.st_mode)) {
	PySys_FormatStderr("%S: %R is a directory, cannot continue\n",
	program_name, filename);
	fclose(fp);
	return 1;
	}

Linked PRs

• gh-142570: Check the file type before skipping the source first line #142709

[nybblista]

@ZeroIntensity @colesbury