From 7fd9f61dbdbe4b0a05c7c66267f06119a16e869a Mon Sep 17 00:00:00 2001 From: Philip Withnall Date: Mon, 13 Aug 2018 14:13:28 +0100 Subject: [PATCH] Avoid calling Standard C string/array functions with NULL arguments glibc string.h declares memcpy() with attribute(nonnull(1,2)), causing calls with NULL arguments to be treated as undefined behaviour. This is consistent with ISO C99 and C11, which state that passing 0 to string functions as an array length does not remove the requirement that the pointer to the array is a valid pointer. gcc -fsanitize=undefined catches this while running OSTree's test suite. Similarly, running the GLib test suite reports similar issues for qsort(), memmove(), memcmp(). (This is a partial cherry-pick of commit e5ed410c8c0fe823883 from GLib.) Signed-off-by: Simon McVittie Bug: https://bugzilla.gnome.org/show_bug.cgi?id=775510 Reviewed-by: Colin Walters --- gvdb-builder.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/gvdb-builder.c b/gvdb-builder.c index c63d1171e..061876845 100644 --- a/gvdb-builder.c +++ b/gvdb-builder.c @@ -293,7 +293,8 @@ file_builder_add_string (FileBuilder *fb, chunk->offset = fb->offset; chunk->size = length; chunk->data = g_malloc (length); - memcpy (chunk->data, string, length); + if (length != 0) + memcpy (chunk->data, string, length); *start = guint32_to_le (fb->offset); *size = guint16_to_le (length);