8000 [3.9] bpo-45831: _Py_DumpASCII() uses a single write() call if possible (GH-29596) by miss-islington · Pull Request #29597 · python/cpython · GitHub
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[3.9] bpo-45831: _Py_DumpASCII() uses a single write() call if possible (GH-29596) #29597

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Merged
merged 1 commit into from
Nov 17, 2021
Merged

[3.9] bpo-45831: _Py_DumpASCII() uses a single write() call if possible (GH-29596) #29597

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5 changes: 5 additions & 0 deletions Misc/NEWS.d/next/Library/2021-11-17-19-25-37.bpo-45831.9-TojK.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
:mod:`faulthandler` can now write ASCII-only strings (like filenames and
function names) with a single write() syscall when dumping a traceback. It
reduces the risk of getting an unreadable dump when two threads or two
processes dump a traceback to the same file (like stderr) at the same time.
Patch by Victor Stinner.
22 changes: 22 additions & 0 deletions Python/traceback.c
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Expand Up @@ -719,6 +719,26 @@ _Py_DumpASCII(int fd, PyObject *text)
truncated = 0;
}

// Is an ASCII string?
if (ascii->state.ascii) {
assert(kind == PyUnicode_1BYTE_KIND);
char *str = data;

int need_escape = 0;
for (i=0; i < size; i++) {
ch = str[i];
if (!(' ' <= ch && ch <= 126)) {
need_escape = 1;
break;
}
}
if (!need_escape) {
// The string can be written with a single write() syscall
_Py_write_noraise(fd, str, size);
goto done;
}
}

for (i=0; i < size; i++) {
if (kind != PyUnicode_WCHAR_KIND)
ch = PyUnicode_READ(kind, data, i);
Expand All @@ -742,6 +762,8 @@ _Py_DumpASCII(int fd, PyObject *text)
_Py_DumpHexadecimal(fd, ch, 8);
}
}

done:
if (truncated) {
PUTS(fd, "...");
}
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