dcwbrown
commented
7 years ago I believe this is fundamentally a problem that should be fixed in the compiler, so
in voc the compiler always generates a dedicated variable for the result and
evaluates the expression on the return statement into it before calling __DEL.
Arguably the compiler should be more intelligent and avoid generating a dedicated
result variable if the return statement does not reference the deleted parameter copy,
but that's quite a big compiler change, so I excused myself by arguing that
the C compiler ought to optimise it to the same code anyway.
The change is here:
https://github.com/dcwbrown/olang.old/commit/e3ca6f6961c4dfbc72f469114f02601cd99c3b0a
-- Dave.
On 2016-08-01 13:33, Oleg N. Cher wrote:
Dear David.
Once you've got rid of alloca in favor of an explicit allocation and deallocation, there was a problem that still doesn't solved, only masked.
PROCEDURE Prefixed(x: OPT.ConstExt; y: ARRAY OF CHAR): BOOLEAN; VAR i: INTEGER; BEGIN i := 0; WHILE x[i+1] = y[i] DO INC(i) END ; RETURN y[i] = 0X END Prefixed;
static BOOLEAN OfrontOPC_Prefixed (OfrontOPT_ConstExt x, CHAR _y, LONGINT ylen) { INTEGER i; DUP(y, ylen, CHAR); i = 0; while ((_x)[X(i + 1, 256)] == y[X(i, y__len)]) { Console_Char(y[X(i, ylen)]); i += 1; } if (y[X(i, y__len)] == 0x00) { ConsoleString((CHAR)" YES! ", (LONGINT)7); } else { ConsoleString((CHAR)" NO! ", (LONGINT)6); } Console_Ln(); DEL(y); return y[X(i, y__len)] == 0x00; }
Look at the last line of the C function. Here is the access into the memory which is already disposed. The way of alloca meant empty definition of DEL(), and everything worked properly. But now DEL() is
define __DEL(x) Platform_OSFree((LONGINT)(uintptr_t)x)
So we have to solve this problem somehow. Such a solution, as below, as you have now, I find unsatisfactory.
PROCEDURE Prefixed(x: OPT.ConstExt; y: ARRAY OF CHAR): BOOLEAN; VAR i: INTEGER; r: BOOLEAN; BEGIN i := 0; WHILE x[i+1] = y[i] DO INC(i) END ; r := y[i] = 0X; RETURN r; END Prefixed;
If you are interested in how I'm doing. Now I will do:
PROCEDURE Prefixed(x: OPT.ConstExt; y: ARRAY [1] OF CHAR): BOOLEAN; VAR i: INTEGER; BEGIN i := 0; WHILE x[i+1] = y[i] DO INC(i) END ; RETURN y[i] = 0X END Prefixed;
And probably I'll go back to the use of alloca. I do not like this, but I did not come up with a better solution.
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Oleg-N-Cher
Dear David.
Once you've got rid of alloca in favor of an explicit allocation and deallocation, there was a problem that still doesn't solved, only masked.
Look at the last line of the C function. Here is the access into the memory which is already disposed. The way of alloca meant empty definition of DEL(), and everything worked properly. But now DEL() is
#define __DEL(x) Platform_OSFree((LONGINT)(uintptr_t)x)So we have to solve this problem somehow. Such a solution, as below, as you have now, I find unsatisfactory.
If you are interested in how I'm doing. Now I will do:
And probably I'll go back to the use of alloca. I do not like this, but I did not come up with a better solution.