toke.c: Don’t depend on sv_force_normal’s good graces

when parsing ‘keyword =>’ with comments or line breaks before the =>.

sv_force_normal will allow modification of read-only values at compile
time.  While this might be convenient, it has resulted in many bugs
elsewhere, so I am trying to change that.  This is a necessary pre-
requisite.

1 files changed, 4 insertions, 0 deletions

diff --git a/toke.c b/toke.c
index 0a1671505d..e31275df93 100644
--- a/toke.c
+++ b/toke.c
@@ -7182,9 +7182,13 @@ Perl_yylex(pTHX)
 		if (*s == '=' && s[1] == '>' && !pkgname) {
 		    op_free(rv2cv_op);
 		    CLINE;
+		    /* This is our own scalar, created a few lines above,
+		       so this is safe. */
+		    SvREADONLY_off(cSVOPx(pl_yylval.opval)->op_sv);
 		    sv_setpv(((SVOP*)pl_yylval.opval)->op_sv, PL_tokenbuf);
 		    if (UTF && !IN_BYTES && is_utf8_string((U8*)PL_tokenbuf, len))
 		      SvUTF8_on(((SVOP*)pl_yylval.opval)->op_sv);
+		    SvREADONLY_on(cSVOPx(pl_yylval.opval)->op_sv);
 		    TERM(WORD);
 		}