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bpo-45831: _Py_DumpASCII() uses a single write() call if possible (GH-29596)

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If the string is ASCII only and doesn't need to escape characters,
write the whole string with a single write() syscall.
This commit is contained in:
Victor Stinner 2021-11-17 21:12:20 +01:00 committed by GitHub
parent e002bbc6cc
commit b919d8105c
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2 changed files with 27 additions and 0 deletions
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5
Misc/NEWS.d/next/Library/2021-11-17-19-25-37.bpo-45831.9-TojK.rst Normal file
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@ -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
Python/traceback.c
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@ -1072,6 +1072,26 @@ _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);
@ -1095,6 +1115,8 @@ _Py_DumpASCII(int fd, PyObject *text)
_Py_DumpHexadecimal(fd, ch, 8);
}
}
done:
if (truncated) {
PUTS(fd, "...");
}