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eval: implement the C ? : operator

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Add the C ternary conditional ? : operator.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
This commit is contained in:
H. Peter Anvin 2018-11-28 13:13:16 -08:00
parent 1722fcf81c
commit 099cc17739
1 changed files with 47 additions and 9 deletions
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56
asm/eval.c
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@ -271,11 +271,12 @@ static int scan(void)
* Grammar parsed is:
*
* expr : bexpr [ WRT expr6 ]
* bexpr : rexp0
* bexpr : cexpr
* cexpr : rexp0 [ {?} bexpr {:} cexpr ]
* rexp0 : rexp1 [ {||} rexp1...]
* rexp1 : rexp2 [ {^^} rexp2...]
* rexp2 : rexp3 [ {&&} rexp3...]
* rexp3 : expr0 [ {=,==,<>,!=,<,>,<=,>=,<=>} expr0 ]
* rexp3 : expr0 [ {=,==,<>,!=,<,>,<=,>=,<=>} expr0... ]
* expr0 : expr1 [ {|} expr1...]
* expr1 : expr2 [ {^} expr2...]
* expr2 : expr3 [ {&} expr3...]
@ -289,6 +290,7 @@ static int scan(void)
* | number
*/
static expr *cexpr(void);
static expr *rexp0(void), *rexp1(void), *rexp2(void), *rexp3(void);
static expr *expr0(void), *expr1(void), *expr2(void), *expr3(void);
@ -297,7 +299,44 @@ static expr *expr4(void), *expr5(void), *expr6(void);
/* This inline is a placeholder for the root of the basic expression */
static inline expr *bexpr(void)
{
return rexp0();
return cexpr();
}
static expr *cexpr(void)
{
expr *e, *f, *g;
e = rexp0();
if (!e)
return NULL;
if (tt == '?') {
scan();
f = bexpr();
if (!f)
return NULL;
if (tt != ':') {
nasm_error(ERR_NONFATAL, "`?' without matching `:'");
return NULL;
}
scan();
g = cexpr();
if (!g)
return NULL;
if (is_simple(e)) {
e = reloc_value(e) ? f : g;
} else if (is_just_unknown(e)) {
e = unknown_expr();
} else {
nasm_error(ERR_NONFATAL, "the left-hand side of `?' must be "
"a scalar value");
}
}
return e;
}
static expr *rexp0(void)
@ -987,7 +1026,7 @@ expr *evaluate(scanner sc, void *scprivate, struct tokenval *tv,
expr *f = NULL;
deadman = 0;
hint = hints;
if (hint)
hint->type = EAH_NOHINT;
@ -998,14 +1037,13 @@ expr *evaluate(scanner sc, void *scprivate, struct tokenval *tv,
tokval = tv;
opflags = fwref;
if (tokval->t_type == TOKEN_INVALID)
scan();
else
tt = tokval->t_type;
while (ntempexprs) /* initialize temporary storage */
nasm_free(tempexprs[--ntempexprs]);
tt = tokval->t_type;
if (tt == TOKEN_INVALID)
scan();
e = bexpr();
if (!e)
return NULL;