scc

commit 67cf8a126f8a96736a156e5edf2164a1669c9544
parent 22a9502ff7a3709825f324d1b717d8bc6d843d32
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Fri, 27 Mar 2026 17:57:26 +0100

cc1: Promote char constants to int

The magnitude of a character constant should be the same
than the result of promoting a char to int, and it means
that in case of having a char with sign we have to convert
it to negative.

Diffstat:
M
src/cmd/scc-cc/cc1/lex.c
 | 
20
++++++++++++++++----
A
tests/cc/execute/0254-litchar.c
 | 
12
++++++++++++
M
tests/cc/execute/scc-tests.lst
 | 
1
+

3 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/src/cmd/scc-cc/cc1/lex.c b/src/cmd/scc-cc/cc1/lex.c
@@ -637,21 +637,26 @@ static int
 character(void)
 {
 	int i, multi = 0;
-	Rune r, d;
-	Type *tp = inttype;
+	Rune r;
+	Type *tp;
 	Symbol *sym;
+	long long d;
+	struct limits *lim;
 
+	tp = chartype;
 	if (*input->p == 'L') {
 		multi = 1;
-		tp = wchartype;
 		input->p++;
+		tp = wchartype;
 	}
 
+	lim = getlimits(tp);
+
 	d = 0;
 	input->p++;
 	for (i = 0; *input->p != '\''; i++) {
 		r = decode(multi);
-		if (r > getlimits(tp)->max.i)
+		if (r > lim->max.i)
 			warn("character too large for enclosing character literal type");
 		d |= r;
 		input->p++;
@@ -663,11 +668,18 @@ character(void)
 	if (i > 1)
 		warn("multi-character character constant");
 
+	if (tp == chartype) {
+		if (tp->prop & TSIGNED && d > lim->max.i)
+			d -= getlimits(uchartype)->max.i + 1;
+		tp = inttype;
+	}
+
 	sym = newsym(NS_IDEN, NULL);
 	sym->u.i = d;
 	sym->type = tp;
 	yylval.sym = sym;
 	tok2str();
+
 	return CONSTANT;
 }
 
diff --git a/tests/cc/execute/0254-litchar.c b/tests/cc/execute/0254-litchar.c
@@ -0,0 +1,12 @@
+int c = '\xff';
+
+int
+main(void)
+{
+	char c = -1;
+
+	if ('\xff' > 0)
+		return !(c > 0);
+	else
+		return !(c < 0);
+}
diff --git a/tests/cc/execute/scc-tests.lst b/tests/cc/execute/scc-tests.lst
@@ -244,3 +244,4 @@
 0251-mul.c
 0252-literal.c
 0253-maxconst.c
+0254-litchar.c