Set %ENV keys using the same byte-string logic as setting %ENV values.

Issue #18636: This extends the work from
613c63b465f01af4e535fdc6c1c17e7470be5aad to %ENV keys. Previously
if you assigned an upgraded string as a key in %ENV, the string’s
internal PV representation was sent to the OS. Now the string is
“soft downgraded” before being given to the OS; if the downgrade
fails--i.e., if the string contains code points above 255--then
a warning is printed, and the string’s utf8 is assigned to the
environment, as happens with %ENV values.

A new internal macro, MgSV, is created to facilitate this work.

1 files changed, 16 insertions, 1 deletions

diff --git a/mg.c b/mg.c
index b1a036ef7b..3355df1b4b 100644
--- a/mg.c
+++ b/mg.c
@@ -1269,9 +1269,24 @@ int
 Perl_magic_setenv(pTHX_ SV *sv, MAGIC *mg)
 {
     STRLEN len = 0, klen;
-    const char * const key = MgPV_const(mg,klen);
+
+    const char *key;
     const char *s = "";
 
+    SV *keysv = MgSV(mg);
+
+    if (keysv == NULL) {
+        key = mg->mg_ptr;
+        klen = mg->mg_len;
+    }
+    else {
+        if (!sv_utf8_downgrade(keysv, /* fail_ok */ TRUE)) {
+            Perl_ck_warner_d(aTHX_ packWARN(WARN_UTF8), "Wide character in %s", "setenv key (encoding to utf8)");
+        }
+
+        key = SvPV_const(keysv,klen);
+    }
+
     PERL_ARGS_ASSERT_MAGIC_SETENV;
 
     SvGETMAGIC(sv);