M70: Avoid CHECK in fpdf_parser_decode.cpp (memcpy empty span)
Given a span of size N, memcpy(dest, &span[N], 0) ought to be a no-op,
but since we compute span[N] before checking for zero length, we hit
an assert. The correct idiom should be to create a sub-span, which
allows specifying N, but only when the size is 0.
Bug: chromium:879910,chromium:889356
Change-Id: Ic6f368109a5c2f1e13a5f638c6a233769e2ad41b
Reviewed-on: https://pdfium-review.googlesource.com/41930
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
(cherry picked from commit 73e97f4fac2f4f591ff62e70377a80fd40b5f6f3)
Reviewed-on: https://pdfium-review.googlesource.com/43271
diff --git a/core/fpdfapi/parser/fpdf_parser_decode.cpp b/core/fpdfapi/parser/fpdf_parser_decode.cpp
index 7a9f798..e8bb21c 100644
--- a/core/fpdfapi/parser/fpdf_parser_decode.cpp
+++ b/core/fpdfapi/parser/fpdf_parser_decode.cpp
@@ -256,7 +256,8 @@
copy_len = buf_left;
memset(*dest_buf + dest_count + copy_len, '\0', delta);
}
- memcpy(*dest_buf + dest_count, &src_span[i + 1], copy_len);
+ auto copy_span = src_span.subspan(i + 1, copy_len);
+ memcpy(*dest_buf + dest_count, copy_span.data(), copy_span.size());
dest_count += src_span[i] + 1;
i += src_span[i] + 2;
} else {
