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gscanner: Avoid undefined behaviour copying between union members

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It’s technically undefined behaviour in C to copy between two
potentially-overlapping regions of memory (just like it is when calling
`memcpy()`). This can easily happen with union members; and the ones in
`GScanner` in particular.

Fix that by copying through an intermediate variable.

Coverity CID: #1427317, 1427340

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>
This commit is contained in:
Philip Withnall 2020-11-03 16:59:36 +00:00
parent e1e32e9b0b
commit add3be2086
1 changed files with 9 additions and 2 deletions
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11
glib/gscanner.c
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@ -1696,12 +1696,19 @@ g_scanner_get_token_i (GScanner *scanner,
scanner->config->int_2_float) scanner->config->int_2_float)
{ {
*token_p = G_TOKEN_FLOAT; *token_p = G_TOKEN_FLOAT;
/* Have to assign through a temporary variable to avoid undefined behaviour
* by copying between potentially-overlapping union members. */
if (scanner->config->store_int64) if (scanner->config->store_int64)
{ {
value_p->v_float = value_p->v_int64; gint64 temp = value_p->v_int64;
value_p->v_float = temp;
} }
else else
value_p->v_float = value_p->v_int; {
gint temp = value_p->v_int;
value_p->v_float = temp;
}
} }
errno = 0; errno = 0;