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Flush stdout and use unbuffered python calls #1342

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Merged
cbm755 merged 1 commit into from
Aug 21, 2026
Merged

Flush stdout and use unbuffered python calls #1342

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9 changes: 7 additions & 2 deletions inst/private/python_header.py
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Original file line number Diff line number Diff line change
@@ -1,10 +1,11 @@
# Copyright (C) 2014-2017, 2019, 2021-2024 Colin B. Macdonald
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2014-2017, 2019, 2021-2024, 2026 Colin B. Macdonald
# Copyright (C) 2019 Mike Miller
# Copyright (C) 2020 Tianyu Chen (billchenchina)
# Copyright (C) 2021 Johannes Maria Frank
# Copyright (C) 2022 Chris Gorman
# Copyright (C) 2022 Alex Vong
# SPDX-License-Identifier: GPL-3.0-or-later
# Copyright (C) 2026 Dmitri A. Sergatskov

# In some cases this code is fed into stdin: two blank lines between
# try-except blocks, no blank lines within each block.
Expand All @@ -27,6 +28,10 @@ def echo_exception_stdout(mystr):
print("<item>\n<f>1003</f>")
print("<f>" + exception_str.replace("&", "&amp;").replace("<", "&lt;").replace(">", "&gt;") + "</f>\n</item>")
print("</list>\n</output_block>\n")
# Python 3.13 and newer do not flush stdout when an exception escapes to
# the interactive interpreter, so callers that "raise" after us would
# leave this block stuck in the buffer (Octave then waits forever).
sys.stdout.flush()

try:
import sympy
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9 changes: 7 additions & 2 deletions inst/private/python_ipc_popen2.m
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Original file line number Diff line number Diff line change
@@ -1,7 +1,8 @@
%% SPDX-License-Identifier: GPL-3.0-or-later
%% Copyright (C) 2014-2019, 2022, 2024 Colin B. Macdonald
%% Copyright (C) 2014-2019, 2022, 2024, 2026 Colin B. Macdonald
%% Copyright (C) 2018, 2020 Mike Miller
%% Copyright (C) 2022 Alex Vong
%% Copyright (C) 2026 Dmitri A. Sergatskov
%%
%% This file is part of OctSymPy.
%%
Expand Down Expand Up @@ -87,7 +88,11 @@
assert_have_python_and_sympy (pyexec)

% formatting matters
args = {'-i', '-c', 'import sys; sys.ps1=''''; sys.ps2='''''};
% '-u': unbuffered stdout: since Python 3.13, the interactive
% interpreter does not flush stdout when an exception escapes to
% the top level, so an output block could sit in the child's
% buffer while we wait forever for it (Issue: pipe deadlock).
args = {'-u', '-i', '-c', 'import sys; sys.ps1=''''; sys.ps2='''''};
[fin, fout, pid] = popen2 (pyexec, args);
fflush (stdout);

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