[perl #76138] perl inadvertently destroys signal handlers as of f746176000

Stop magic applied to $!, %SIG, et al. from applying to similarly-
named variables in other packages.

1 files changed, 50 insertions, 21 deletions

diff --git a/gv.c b/gv.c
index 6f63f4bd8f..72016bf6d5 100644
--- a/gv.c
+++ b/gv.c
@@ -1204,33 +1204,19 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
         GvMULTI_on(gv) ;
 
     /* set up magic where warranted */
-    if (len > 1) {
-#ifndef EBCDIC
-	if (*name > 'V' ) {
-	    NOOP;
-	    /* Nothing else to do.
-	       The compiler will probably turn the switch statement into a
-	       branch table. Make sure we avoid even that small overhead for
-	       the common case of lower case variable names.  */
-	} else
-#endif
-	{
+    if (stash != PL_defstash) { /* not the main stash */
+	/* We only have to check for four names here: EXPORT, ISA, OVERLOAD
+	   and VERSION. All the others apply only to the main stash. */
+	if (len > 1) {
 	    const char * const name2 = name + 1;
 	    switch (*name) {
-	    case 'A':
-		if (strEQ(name2, "RGV")) {
-		    IoFLAGS(GvIOn(gv)) |= IOf_ARGV|IOf_START;
-		}
-		else if (strEQ(name2, "RGVOUT")) {
-		    GvMULTI_on(gv);
-		}
-		break;
 	    case 'E':
 		if (strnEQ(name2, "XPORT", 5))
 		    GvMULTI_on(gv);
 		break;
 	    case 'I':
-		if (strEQ(name2, "SA")) {
+		if (strEQ(name2, "SA"))
+		magicalize_isa: {
 		    AV* const av = GvAVn(gv);
 		    GvMULTI_on(gv);
 		    sv_magic(MUTABLE_SV(av), MUTABLE_SV(gv), PERL_MAGIC_isa,
@@ -1253,12 +1239,55 @@ Perl_gv_fetchpvn_flags(pTHX_ const char *nambeg, STRLEN full_len, I32 flags,
 		}
 		break;
 	    case 'O':
-		if (strEQ(name2, "VERLOAD")) {
+		if (strEQ(name2, "VERLOAD"))
+		magicalize_overload: {
 		    HV* const hv = GvHVn(gv);
 		    GvMULTI_on(gv);
 		    hv_magic(hv, NULL, PERL_MAGIC_overload);
 		}
 		break;
+	    case 'V':
+		if (strEQ(name2, "ERSION"))
+		    GvMULTI_on(gv);
+		break;
+	    }
+	}
+    }
+    else if (len > 1) {
+#ifndef EBCDIC
+	if (*name > 'V' ) {
+	    NOOP;
+	    /* Nothing else to do.
+	       The compiler will probably turn the switch statement into a
+	       branch table. Make sure we avoid even that small overhead for
+	       the common case of lower case variable names.  */
+	} else
+#endif
+	{
+	    const char * const name2 = name + 1;
+	    switch (*name) {
+	    case 'A':
+		if (strEQ(name2, "RGV")) {
+		    IoFLAGS(GvIOn(gv)) |= IOf_ARGV|IOf_START;
+		}
+		else if (strEQ(name2, "RGVOUT")) {
+		    GvMULTI_on(gv);
+		}
+		break;
+	    case 'E':
+		if (strnEQ(name2, "XPORT", 5))
+		    GvMULTI_on(gv);
+		break;
+	    case 'I':
+		if (strEQ(name2, "SA")) {
+		    goto magicalize_isa;
+		}
+		break;
+	    case 'O':
+		if (strEQ(name2, "VERLOAD")) {
+		    goto magicalize_overload;
+		}
+		break;
 	    case 'S':
 		if (strEQ(name2, "IG")) {
 		    HV *hv;