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dtc: Warning rather than error on possible truncation of cell values

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We always evaluate integer values in cell arrays as 64-bit quantities, then
truncate to the size of the array cells (32-bit by default).  However to
detect accidental truncation of meaningful values, we give an error if the
truncated portion isn't either all 0 or all 1 bits.  However, this can
still give counterintuitive errors.  For if the user is thinking in 2's
complement 32-bit arithmetic (which would be quite natural), then they'd
expect the expression (-0xffffffff-2) to evaluate to -1 (0xffffffff).
However in 64-bit it evaluates to 0xfffffffeffffffff which does truncate
to the expected value but trips this error message.

Because of this reduce the error to only a warnings, with a somewhat more
helpful message.

Fixes: https://github.com/dgibson/dtc/issues/74

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
David Gibson 2022-11-21 14:18:44 +11:00
parent 55778a03df
commit 2cd89f862c
4 changed files with 27 additions and 3 deletions
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11
dtc-parser.y
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@ -404,9 +404,14 @@ arrayprefix:
* within the mask to one (i.e. | in the
* mask), all bits are one.
*/
if (($2 > mask) && (($2 | mask) != -1ULL))
ERROR(&@2, "Value out of range for"
" %d-bit array element", $1.bits);
if (($2 > mask) && (($2 | mask) != -1ULL)) {
char *loc = srcpos_string(&@2);
fprintf(stderr,
"WARNING: %s: Value 0x%016" PRIx64
" truncated to 0x%0*" PRIx64 "\n",
loc, $2, $1.bits / 4, ($2 & mask));
free(loc);
}
}
$$.data = data_append_integer($1.data, $2, $1.bits);