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fix for #1941, taken from 22d435b689

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This commit is contained in:
mrdudz 2023-01-28 12:29:05 +01:00
parent 60f56c43c7
commit 1764b7aca9
2 changed files with 48 additions and 17 deletions
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37
src/cc65/shiftexpr.c
View File

@ -169,27 +169,21 @@ void ShiftExpr (struct ExprDesc* Expr)
}
}
/* If the shift count is zero, nothing happens. If the left hand
** side is a constant, the result is constant.
*/
if (Expr2.IVal == 0 || lconst) {
/* Set the type */
/* If the left hand side is a constant, the result is constant */
if (lconst) {
/* Set the result type */
Expr->Type = ResultType;
if (lconst) {
/* Evaluate the result */
switch (Tok) {
case TOK_SHL: Expr->IVal <<= Expr2.IVal; break;
case TOK_SHR: Expr->IVal >>= Expr2.IVal; break;
default: /* Shutup gcc */ break;
}
/* Limit the calculated value to the range of its type */
LimitExprValue (Expr, 1);
/* Evaluate the result */
switch (Tok) {
case TOK_SHL: Expr->IVal <<= Expr2.IVal; break;
case TOK_SHR: Expr->IVal >>= Expr2.IVal; break;
default: /* Shutup gcc */ break;
}
/* Limit the calculated value to the range of its type */
LimitExprValue (Expr, 1);
/* Result is already got, remove the generated code */
RemoveCode (&Mark1);
@ -197,6 +191,15 @@ void ShiftExpr (struct ExprDesc* Expr)
continue;
}
/* If the shift count is zero, nothing happens */
if (Expr2.IVal == 0) {
/* Result is already got, remove the pushing code */
RemoveCode (&Mark2);
/* Be sure to mark the value as in the primary */
goto MakeRVal;
}
/* If we're shifting an integer or unsigned to the right, the lhs
** has a quasi-const address, and the shift count is larger than 8,
** we can load just the high byte as a char with the correct

28
test/val/bug1941-shift-by-zero.c Normal file
View File

@ -0,0 +1,28 @@
/* Bug 1941 - Bitwise shift char types by 0 count results in out-of-range access */
#include <stdio.h>
#include <stdint.h>
uint8_t foo = 42U; /* "Low byte" */
uint8_t goo = 1U; /* "High byte" - you need it to reproduce the issue */
int16_t bar = 256; /* ...or just do it with this */
_Static_assert (sizeof (foo >> 0) == sizeof (int), "Shift result should be int-promoted");
_Static_assert (sizeof ((int8_t)bar << 0) == sizeof (int), "Shift result should be int-promoted");
unsigned failures;
int main(void)
{
if (foo >> 0 != foo) {
++failures;
printf("foo failed\n");
}
if ((int8_t)bar << 0 != (int8_t)bar) {
++failures;
printf("bar failed\n");
}
return failures;
}