[gcc(refs/users/marxin/heads/D-fix-ubsan)] D: fix UBSAN

[Martin Liska]

https://gcc.gnu.org/g:c72e2c3a0a2dbfe3c1e4edbc9754f65bb4462bac

commit c72e2c3a0a2dbfe3c1e4edbc9754f65bb4462bac
Author: Martin Liska <mliska@suse.cz>
Date:   Mon Dec 6 13:02:22 2021 +0100

    D: fix UBSAN
    
    Fixes:
    gcc/d/expr.cc:2596:9: runtime error: null pointer passed as argument 2, which is declared to never be null
    
    gcc/d/ChangeLog:
    
            * expr.cc: Call memcpy only when length != 0.

Diff:
---
 gcc/d/expr.cc | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/gcc/d/expr.cc b/gcc/d/expr.cc
index 31680564bdd..22acbc07cde 100644
--- a/gcc/d/expr.cc
+++ b/gcc/d/expr.cc
@@ -2593,7 +2593,8 @@ public:
 	/* Copy the string contents to a null terminated string.  */
 	dinteger_t length = (e->len * e->sz);
 	char *string = XALLOCAVEC (char, length + 1);
-	memcpy (string, e->string, length);
+	if (length > 0)
+	  memcpy (string, e->string, length);
 	string[length] = '\0';
 
 	/* String value and type includes the null terminator.  */