Merge bitcoin-core#1482: build: Clean up handling of module dependencies

e682267 build: Error if required module explicitly off (Tim Ruffing)
89ec583 build: Clean up handling of module dependencies (Tim Ruffing)

Pull request description:

  This is a cleanup which makes it easier to add further modules with dependencies, e.g., in bitcoin-core#1452. The diff looks larger than it is because I also reordered the modules and made the order consistent between CMake and autotools.

  (We noticed that the current logic could be improved in BlockstreamResearch/secp256k1-zkp#275.)

ACKs for top commit:
  jonasnick:
    ACK e682267
  hebasto:
    ACK e682267.

Tree-SHA512: 040e791e5b5b9b8845a39632633a45ca759391455910bdefba2b7b77c6340e65df6eda18199ae2ad65c30ee2fc6630471437aec143c26fe09ae4c11409a37622

CMakeLists.txt

@@ -51,29 +51,40 @@ endif()
 
 option(SECP256K1_INSTALL "Enable installation." ${PROJECT_IS_TOP_LEVEL})
 
-option(SECP256K1_ENABLE_MODULE_ECDH "Enable ECDH module." ON)
-if(SECP256K1_ENABLE_MODULE_ECDH)
-  add_compile_definitions(ENABLE_MODULE_ECDH=1)
-endif()
+## Modules
 
+# We declare all options before processing them, to make sure we can express
+# dependendencies while processing.
+option(SECP256K1_ENABLE_MODULE_ECDH "Enable ECDH module." ON)
 option(SECP256K1_ENABLE_MODULE_RECOVERY "Enable ECDSA pubkey recovery module." OFF)
-if(SECP256K1_ENABLE_MODULE_RECOVERY)
-  add_compile_definitions(ENABLE_MODULE_RECOVERY=1)
-endif()
-
 option(SECP256K1_ENABLE_MODULE_EXTRAKEYS "Enable extrakeys module." ON)
 option(SECP256K1_ENABLE_MODULE_SCHNORRSIG "Enable schnorrsig module." ON)
+option(SECP256K1_ENABLE_MODULE_ELLSWIFT "Enable ElligatorSwift module." ON)
+
+# Processing must be done in a topological sorting of the dependency graph
+# (dependent module first).
+if(SECP256K1_ENABLE_MODULE_ELLSWIFT)
+  add_compile_definitions(ENABLE_MODULE_ELLSWIFT=1)
+endif()
+
 if(SECP256K1_ENABLE_MODULE_SCHNORRSIG)
+  if(DEFINED SECP256K1_ENABLE_MODULE_EXTRAKEYS AND NOT SECP256K1_ENABLE_MODULE_EXTRAKEYS)
+    message(FATAL_ERROR "Module dependency error: You have disabled the extrakeys module explicitly, but it is required by the schnorrsig module.")
+  endif()
   set(SECP256K1_ENABLE_MODULE_EXTRAKEYS ON)
   add_compile_definitions(ENABLE_MODULE_SCHNORRSIG=1)
 endif()
+
 if(SECP256K1_ENABLE_MODULE_EXTRAKEYS)
   add_compile_definitions(ENABLE_MODULE_EXTRAKEYS=1)
 endif()
 
-option(SECP256K1_ENABLE_MODULE_ELLSWIFT "Enable ElligatorSwift module." ON)
-if(SECP256K1_ENABLE_MODULE_ELLSWIFT)
-  add_compile_definitions(ENABLE_MODULE_ELLSWIFT=1)
+if(SECP256K1_ENABLE_MODULE_RECOVERY)
+  add_compile_definitions(ENABLE_MODULE_RECOVERY=1)
+endif()
+
+if(SECP256K1_ENABLE_MODULE_ECDH)
+  add_compile_definitions(ENABLE_MODULE_ECDH=1)
 endif()
 
 option(SECP256K1_USE_EXTERNAL_DEFAULT_CALLBACKS "Enable external default callback functions." OFF)

configure.ac

@@ -387,29 +387,32 @@ SECP_CFLAGS="$SECP_CFLAGS $WERROR_CFLAGS"
 ### Handle module options
 ###
 
-if test x"$enable_module_ecdh" = x"yes"; then
-  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ECDH=1"
-fi
-
-if test x"$enable_module_recovery" = x"yes"; then
-  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_RECOVERY=1"
+# Processing must be done in a reverse topological sorting of the dependency graph
+# (dependent module first).
+if test x"$enable_module_ellswift" = x"yes"; then
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ELLSWIFT=1"
 fi
 
 if test x"$enable_module_schnorrsig" = x"yes"; then
-  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_SCHNORRSIG=1"
+  if test x"$enable_module_extrakeys" = x"no"; then
+    AC_MSG_ERROR([Module dependency error: You have disabled the extrakeys module explicitly, but it is required by the schnorrsig module.])
+  fi
   enable_module_extrakeys=yes
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_SCHNORRSIG=1"
 fi
 
-if test x"$enable_module_ellswift" = x"yes"; then
-  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ELLSWIFT=1"
-fi
-
-# Test if extrakeys is set after the schnorrsig module to allow the schnorrsig
-# module to set enable_module_extrakeys=yes
 if test x"$enable_module_extrakeys" = x"yes"; then
   SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_EXTRAKEYS=1"
 fi
 
+if test x"$enable_module_recovery" = x"yes"; then
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_RECOVERY=1"
+fi
+
+if test x"$enable_module_ecdh" = x"yes"; then
+  SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DENABLE_MODULE_ECDH=1"
+fi
+
 if test x"$enable_external_default_callbacks" = x"yes"; then
   SECP_CONFIG_DEFINES="$SECP_CONFIG_DEFINES -DUSE_EXTERNAL_DEFAULT_CALLBACKS=1"
 fi