Merge bitcoin-core/secp256k1#995: build: stop treating schnorrsig, extrakeys modules as experimental

7f09d0f README: mention that ARM assembly is experimental (Jonas Nick)
80cf4ee build: stop treating schnorrsig, extrakeys modules as experimental (Jonas Nick)

Pull request description:

  Fixes bitcoin#992

ACKs for top commit:
  real-or-random:
    ACK 7f09d0f
  fanquake:
    ACK 7f09d0f - When this is in, I think we'll do a subtree update in Core, and prune some build cruft on our side.

Tree-SHA512: 13deb82dcca88bacb2cd5c1c589a8d4af2277c4d675262337ae4d7e93eb41d43825dda4945ca1c202c36aaa2e6fd42de9c6d711fe8d71bce578368281db698b2

Author: real-or-random

.cirrus.yml

@@ -67,12 +67,12 @@ task:
   << : *LINUX_CONTAINER
   matrix: &ENV_MATRIX
     - env: {WIDEMUL:  int64,  RECOVERY: yes}
-    - env: {WIDEMUL:  int64,                 ECDH: yes, EXPERIMENTAL: yes, SCHNORRSIG: yes}
+    - env: {WIDEMUL:  int64,                 ECDH: yes, SCHNORRSIG: yes}
     - env: {WIDEMUL: int128}
-    - env: {WIDEMUL: int128,  RECOVERY: yes,            EXPERIMENTAL: yes, SCHNORRSIG: yes}
-    - env: {WIDEMUL: int128,                 ECDH: yes, EXPERIMENTAL: yes, SCHNORRSIG: yes}
+    - env: {WIDEMUL: int128,  RECOVERY: yes,            SCHNORRSIG: yes}
+    - env: {WIDEMUL: int128,                 ECDH: yes, SCHNORRSIG: yes}
     - env: {WIDEMUL: int128,  ASM: x86_64}
-    - env: {                  RECOVERY: yes,            EXPERIMENTAL: yes, SCHNORRSIG: yes}
+    - env: {                  RECOVERY: yes,            SCHNORRSIG: yes}
     - env: {BUILD: distcheck, WITH_VALGRIND: no, CTIMETEST: no, BENCH: no}
     - env: {CPPFLAGS: -DDETERMINISTIC}
     - env: {CFLAGS: -O0, CTIMETEST: no}
@@ -95,7 +95,6 @@ task:
     HOST: i686-linux-gnu
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
   matrix:
     - env:
@@ -178,7 +177,6 @@ task:
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   << : *MERGE_BASE
@@ -198,12 +196,11 @@ task:
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   matrix:
     - env: {}
-    - env: {ASM: arm}
+    - env: {EXPERIMENTAL: yes, ASM: arm}
   << : *MERGE_BASE
   test_script:
     - ./ci/cirrus.sh
@@ -219,7 +216,6 @@ task:
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   << : *MERGE_BASE
@@ -237,7 +233,6 @@ task:
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   << : *MERGE_BASE
@@ -255,7 +250,6 @@ task:
     WITH_VALGRIND: no
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   << : *MERGE_BASE
@@ -269,7 +263,6 @@ task:
   env:
     ECDH: yes
     RECOVERY: yes
-    EXPERIMENTAL: yes
     SCHNORRSIG: yes
     CTIMETEST: no
   matrix:
@@ -317,7 +310,6 @@ task:
     CC: gcc
     MAKEFLAGS: -j4 CC=g++ CFLAGS=-fpermissive\ -g
     WERROR_CFLAGS:
-    EXPERIMENTAL: yes
     ECDH: yes
     RECOVERY: yes
     SCHNORRSIG: yes

README.md

@@ -17,9 +17,7 @@ Features:
 * Suitable for embedded systems.
 * Optional module for public key recovery.
 * Optional module for ECDH key exchange.
-* Optional module for Schnorr signatures according to [BIP-340](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki) (experimental).
-
-Experimental features have not received enough scrutiny to satisfy the standard of quality of this library but are made available for testing and review by the community. The APIs of these features should not be considered stable.
+* Optional module for Schnorr signatures according to [BIP-340](https://github.com/bitcoin/bips/blob/master/bip-0340.mediawiki).
 
 Implementation details
 ----------------------
@@ -35,6 +33,7 @@ Implementation details
   * Optimized implementation of arithmetic modulo the curve's field size (2^256 - 0x1000003D1).
     * Using 5 52-bit limbs (including hand-optimized assembly for x86_64, by Diederik Huys).
     * Using 10 26-bit limbs (including hand-optimized assembly for 32-bit ARM, by Wladimir J. van der Laan).
+      * This is an experimental feature that has not received enough scrutiny to satisfy the standard of quality of this library but is made available for testing and review by the community.
 * Scalar operations
   * Optimized implementation without data-dependent branches of arithmetic modulo the curve's order.
     * Using 4 64-bit limbs (relying on __int128 support in the compiler).
@@ -72,7 +71,6 @@ libsecp256k1 is built using autotools:
 Usage examples
 -----------
   Usage examples can be found in the [examples](examples) directory. To compile them you need to configure with `--enable-examples`.
-  For experimental modules, you will also need `--enable-experimental` as well as a flag for each individual module, e.g. `--enable-module-ecdh`.
   * [ECDSA example](examples/ecdsa.c)
   * [Schnorr Signatures example](examples/schnorr.c)
   * [Deriving a shared secret(ECDH) example](examples/ecdh.c)

configure.ac

@@ -149,11 +149,11 @@ AC_ARG_ENABLE(module_recovery,
     [SECP_SET_DEFAULT([enable_module_recovery], [no], [yes])])
 
 AC_ARG_ENABLE(module_extrakeys,
-    AS_HELP_STRING([--enable-module-extrakeys],[enable extrakeys module (experimental)]), [],
+    AS_HELP_STRING([--enable-module-extrakeys],[enable extrakeys module]), [],
     [SECP_SET_DEFAULT([enable_module_extrakeys], [no], [yes])])
 
 AC_ARG_ENABLE(module_schnorrsig,
-    AS_HELP_STRING([--enable-module-schnorrsig],[enable schnorrsig module (experimental)]), [],
+    AS_HELP_STRING([--enable-module-schnorrsig],[enable schnorrsig module]), [],
     [SECP_SET_DEFAULT([enable_module_schnorrsig], [no], [yes])])
 
 AC_ARG_ENABLE(external_default_callbacks,
@@ -364,16 +364,8 @@ if test x"$enable_experimental" = x"yes"; then
   AC_MSG_NOTICE([******])
   AC_MSG_NOTICE([WARNING: experimental build])
   AC_MSG_NOTICE([Experimental features do not have stable APIs or properties, and may not be safe for production use.])
-  AC_MSG_NOTICE([Building extrakeys module: $enable_module_extrakeys])
-  AC_MSG_NOTICE([Building schnorrsig module: $enable_module_schnorrsig])
   AC_MSG_NOTICE([******])
 else
-  if test x"$enable_module_extrakeys" = x"yes"; then
-    AC_MSG_ERROR([extrakeys module is experimental. Use --enable-experimental to allow.])
-  fi
-  if test x"$enable_module_schnorrsig" = x"yes"; then
-    AC_MSG_ERROR([schnorrsig module is experimental. Use --enable-experimental to allow.])
-  fi
   if test x"$set_asm" = x"arm"; then
     AC_MSG_ERROR([ARM assembly optimization is experimental. Use --enable-experimental to allow.])
   fi