Test C++17 byte change with dry runs from various projects

[noloader]

I'd like to use this issue to track some dry runs of the proposed change due to C++17, std::byte and collisions with Crypto++ byte . We've tested the change with toy programs, and we would like to solicit feedback from real projects using Crypto++.

The 3 second tour is as follows. From 10,000 feet, Crypto++ plans on moving byte from the global namespace into the Crypto++ namespace. The move creates a void in user programs, and it can be filled by (1) using CryptoPP::byte instead of byte; (2) using byte = CryptoPP::byte; (C++11 and above); or (3) typedef unsigned char byte; (C++03 and above). If possible, you should use (3) - supply your own typedef.

1. Make this change to Crypto++ library:

$ cat byte.diff
diff --git a/config.h b/config.h
index 291b148..92a6b84 100644
--- a/config.h
+++ b/config.h
@@ -194,10 +194,12 @@ namespace CryptoPP { }
 #      define __USE_W32_SOCKETS
 #endif

-typedef unsigned char byte;
+// typedef unsigned char byte;
+#define CRYPTOPP_NO_GLOBAL_BYTE 1

 NAMESPACE_BEGIN(CryptoPP)

+typedef unsigned char byte;
 typedef unsigned short word16;
 typedef unsigned int word32;

2. Optionally, make this change in the user program or project using Crypto++:

#include <cryptopp/config.h>
#if (CRYPTOPP_VERSION >= 600) && (__cplusplus >= 201103L)
    using byte = CryptoPP::byte;
#else
    typedef unsigned char byte;
#endif

// Alternately, use CryptoPP::byte everywhere instead of ::byte

3. Use GCC 7
   • Fedora 26 ships with it
   • Debian Buster with apt-get install gcc-7 g++-7
4. Use -std=c++17
   • Build Crypto++ library with -std=c++17 (will be OK)
   • Build project with -std=c++17 (report your problems)

For item (4), Build Crypto++ library with -std=c++17 , perform the following:

$ CXX=g++-7 CXXFLAGS="-DNDEBUG -g2 -O3 -std=c++17" make -j 2

CRYPTOPP_NO_GLOBAL_BYTE is a convenience item for those supporting multiple versions of Crypto++. It is really only needed for the gap between the 5.6.5 release and the 6.0 release because Master currently uses #define CRYPTOPP_VERSION 600. But signalling it through a define is painless. Related, see Release Versioning | Post-Release Increment on the Crypto++ wiki.

Please report problems and work-arounds below. If you had problems, please state if it was due to using namespace std;. Work-arounds are suggested at std::byte | Fixing Programs on the Crypto++ wiki.

---

Here are folks who may be able to help with the dry run. Listing their name generates the GitHub notification. The names were gathered from a GitHub search for projects with activity in 2016 and 2017. @anonimal, @swarren, @mmoss, @zooko, @huahang, @prakhs123, @pld-linux, @sechaser, @elementrem, @xItsMe, @Mowje, @NickNaso, @cawka, @wyrover, @vunguyenthe, @vster, @alphaemmeo, @smasherprog, @pschord, @psforever, @harrywye, @vcpkgs, @tpgxyz, @luofujie, @badforlabor, @smasherprog, @riebl, @DonAlonzo, @amani-lei, @xy12423, @Cyberunner23, @Xiao-Chong, @coderChenY, @familyld, @firngrod, @tcolligan-ap, @dotman14, @reganheath, @motioncity, @MarcelRaad, @DevJPM, @mouse07410, @denisbider, @gcsideal, @buildroot-auto-update, @woodsts, @snickl.

If you need to update your Crypto++ clone, then issue git pull. If you need to reset your Crypto++ clone to upstream/master, then see reset-fork.sh provided in Crypto++ Master.

The change to accommodate C++17 and std::byte will be available in Master and eventually Crypto++ 6.0. The change requires a major version bump.

---

For documentation purposes, see the following on the Crypto++ User mailing list:

• PR 438: Use ::byte instead of byte
• Merge byte change (::byte → CryptoPP::byte)

[noloader]

Here are the results from Pycryptopp. It appears Pycryptopp did not import the entire std:: or CryptoPP:: namespace, so they avoided the collisions that would have occurred in C++17. The project was in very good shape, and it only needed a few surgical fixes.

Pycryptopp needed the following due to the upcoming Crypto++ changes. The changes made to Pycryptopp are compatible with the old version (::byte) and new version (CryptoPP::byte) of the Crypto++ library.

$ cat pycryptopp.diff
diff --git a/src/pycryptopp/cipher/aesmodule.cpp b/src/pycryptopp/cipher/aesmodule.cpp
index 360827d..3d0b95a 100644
--- a/src/pycryptopp/cipher/aesmodule.cpp
+++ b/src/pycryptopp/cipher/aesmodule.cpp
@@ -20,6 +20,9 @@ typedef int Py_ssize_t;
 #include <src-cryptopp/aes.h>
 #endif

+// https://github.com/weidai11/cryptopp/issues/442
+typedef unsigned char byte;
+
 static const char*const aes___doc__ = "_aes counter mode cipher\n\
 You are advised to run aes.start_up_self_test() after importing this module.";

diff --git a/src/pycryptopp/cipher/xsalsa20module.cpp b/src/pycryptopp/cipher/xsalsa20module.cpp
index ab29787..a0b7c71 100644
--- a/src/pycryptopp/cipher/xsalsa20module.cpp
+++ b/src/pycryptopp/cipher/xsalsa20module.cpp
@@ -16,6 +16,9 @@ typedef int Py_ssize_t;
 #include <src-cryptopp/salsa.h>
 #endif

+// https://github.com/weidai11/cryptopp/issues/442
+typedef unsigned char byte;
+
 static const char* const xsalsa20__doc__ = "_xsalsa20 cipher";

 static PyObject *xsalsa20_error;
diff --git a/src/pycryptopp/hash/sha256module.cpp b/src/pycryptopp/hash/sha256module.cpp
index bf9d8e3..8272e6c 100644
--- a/src/pycryptopp/hash/sha256module.cpp
+++ b/src/pycryptopp/hash/sha256module.cpp
@@ -21,6 +21,9 @@ typedef int Py_ssize_t;
 #include <src-cryptopp/filters.h>
 #endif

+// https://github.com/weidai11/cryptopp/issues/442
+typedef unsigned char byte;
+
 static const char*const sha256___doc__ = "_sha256 hash function";

 static PyObject *sha256_error;

[anonimal]

Hi @noloader. I've been watching this byte issue unfold and we remain unaffected. Thank you for the ping 😄

[noloader]

The change was checked in at Commit 00f9818b5d8e5aeb.