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gh-129813, PEP 782: Set invalid bytes in PyBytesWriter (#139054)

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Initialize the buffer with 0xFF byte pattern when creating a writer
object, but also when resizing/growing the writer.
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Victor Stinner 2025-09-17 16:58:32 +01:00 • committed by GitHub
parent 82e1920a01
commit c72ffe71f1
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GPG key ID: B5690EEEBB952194
1 changed files with 15 additions and 6 deletions
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21
Objects/bytesobject.c
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@ -3805,12 +3805,12 @@ byteswriter_resize(PyBytesWriter *writer, Py_ssize_t size, int overallocate)
{ {
assert(size >= 0); assert(size >= 0);
if (size <= byteswriter_allocated(writer)) { Py_ssize_t old_allocated = byteswriter_allocated(writer);
if (size <= old_allocated) {
return 0; return 0;
} }
overallocate &= writer->overallocate; if (overallocate & writer->overallocate) {
if (overallocate) {
if (size <= (PY_SSIZE_T_MAX - size / OVERALLOCATE_FACTOR)) { if (size <= (PY_SSIZE_T_MAX - size / OVERALLOCATE_FACTOR)) {
size += size / OVERALLOCATE_FACTOR; size += size / OVERALLOCATE_FACTOR;
} }
@ -3849,6 +3849,15 @@ byteswriter_resize(PyBytesWriter *writer, Py_ssize_t size, int overallocate)
writer->small_buffer, writer->small_buffer,
sizeof(writer->small_buffer)); sizeof(writer->small_buffer));
} }
#ifdef Py_DEBUG
Py_ssize_t allocated = byteswriter_allocated(writer);
if (overallocate && allocated > old_allocated) {
memset(byteswriter_data(writer) + old_allocated, 0xff,
allocated - old_allocated);
}
#endif
return 0; return 0;
} }
@ -3869,9 +3878,6 @@ byteswriter_create(Py_ssize_t size, int use_bytearray)
return NULL; return NULL;
} }
} }
#ifdef Py_DEBUG
memset(writer->small_buffer, 0xff, sizeof(writer->small_buffer));
#endif
writer->obj = NULL; writer->obj = NULL;
writer->size = 0; writer->size = 0;
writer->use_bytearray = use_bytearray; writer->use_bytearray = use_bytearray;
@ -3884,6 +3890,9 @@ byteswriter_create(Py_ssize_t size, int use_bytearray)
} }
writer->size = size; writer->size = size;
} }
#ifdef Py_DEBUG
memset(byteswriter_data(writer), 0xff, byteswriter_allocated(writer));
#endif
return writer; return writer;
} }