Work around language and compiler bug in memcpy, etc.
Most C standard library functions are undefined if passed NULL, even
when the corresponding length is zero. This gives them (and, in turn,
all functions which call them) surprising behavior on empty arrays.
Some compilers will miscompile code due to this rule. See also
https://www.imperialviolet.org/2016/06/26/nonnull.html
Add OPENSSL_memcpy, etc., wrappers which avoid this problem.
BUG=23
Change-Id: I95f42b23e92945af0e681264fffaf578e7f8465e
Reviewed-on: https://boringssl-review.googlesource.com/12928
Commit-Queue: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/STYLE.md b/STYLE.md
index 4c88945..4b377e7 100644
--- a/STYLE.md
+++ b/STYLE.md
@@ -45,6 +45,16 @@
Rather than `malloc()` and `free()`, use the wrappers `OPENSSL_malloc()`
and `OPENSSL_free()`. Use the standard C `assert()` function freely.
+Use the following wrappers, found in `crypto/internal.h` instead of the
+corresponding C standard library functions. They behave the same but avoid
+confusing undefined behavior.
+
+* `OPENSSL_memchr`
+* `OPENSSL_memcmp`
+* `OPENSSL_memcpy`
+* `OPENSSL_memmove`
+* `OPENSSL_memset`
+
For new constants, prefer enums when the values are sequential and typed
constants for flags. If adding values to an existing set of `#define`s,
continue with `#define`.
