scc

commit 28c274e634e5bb1a8a99ee403f1373b6db7fcd07
parent 40275b12f4b192d63d7d6702fd3caaa8eb3f5bc5
Author: Roberto E. Vargas Caballero <k0ga@shike2.net>
Date:   Wed, 18 Feb 2026 19:45:06 +0100

cc1: Warn only in different macro redefinitions

The standard says that redefining a macro with a different value is undefined
behaviour. Scc uses to warn in any redefinition of macros, but as there are
some projects that like to redefine them continously this generated too much
noise, and this commit moved the warning to only when the defintion is different.

Diffstat:
M
src/cmd/scc-cc/cc1/cpp.c
 | 
17
++++++++++-------

1 file changed, 10 insertions(+), 7 deletions(-)
diff --git a/src/cmd/scc-cc/cc1/cpp.c b/src/cmd/scc-cc/cc1/cpp.c
@@ -645,13 +645,6 @@ define(void)
 		return;
 	}
 	sym = yylval.sym;
-	if (sym->flags & SDECLARED) {
-		warn("'%s' redefined", yytext);
-		free(sym->u.s);
-	} else {
-		sym = install(NS_CPP, sym);
-		sym->flags |= SDECLARED|SSTRING;
-	}
 
 	namespace = NS_IDEN;       /* Avoid polution in NS_CPP */
 	if ((n = getpars(args)) == NR_MACROARG)
@@ -662,6 +655,16 @@ define(void)
 	sprintf(buff, "%02d#", n);
 	if (!getdefs(args, n, buff+3, LINESIZ-3))
 		goto delete;
+
+	if (sym->flags & SDECLARED) {
+		if (strcmp(sym->u.s, buff) != 0)
+			warn("'%s' redefined", sym->name);
+		free(sym->u.s);
+	} else {
+		sym = install(NS_CPP, sym);
+		sym->flags |= SDECLARED|SSTRING;
+	}
+
 	sym->u.s = xstrdup(buff);
 	DBG("MACRO '%s' defined as '%s'", sym->name, buff);
 	return;