I encountered this error when building with the --disable-bittorrent flag with the commit 3330110.

make all-recursive
make[1]: Entering directory '/home/acer/aria2/aria2'
Making all in po
make[2]: Entering directory '/home/acer/aria2/aria2/po'
make[2]: Leaving directory '/home/acer/aria2/aria2/po'
Making all in lib
make[2]: Entering directory '/home/acer/aria2/aria2/lib'
make[2]: Nothing to be done for 'all'.
make[2]: Leaving directory '/home/acer/aria2/aria2/lib'
Making all in deps
make[2]: Entering directory '/home/acer/aria2/aria2/deps'
make[3]: Entering directory '/home/acer/aria2/aria2/deps'
make[3]: Nothing to be done for 'all-am'.
make[3]: Leaving directory '/home/acer/aria2/aria2/deps'
make[2]: Leaving directory '/home/acer/aria2/aria2/deps'
Making all in src
make[2]: Entering directory '/home/acer/aria2/aria2/src'
Making all in includes
make[3]: Entering directory '/home/acer/aria2/aria2/src/includes'
make[3]: Nothing to be done for 'all'.
make[3]: Leaving directory '/home/acer/aria2/aria2/src/includes'
make[3]: Entering directory '/home/acer/aria2/aria2/src'
CXX main.o
CXX A2STR.lo
CXX AbstractAuthResolver.lo
CXX AbstractCommand.lo
CXX AbstractDiskWriter.lo
CXX AbstractHttpServerResponseCommand.lo
CXX AbstractOptionHandler.lo
CXX AbstractProxyRequestCommand.lo
CXX AbstractProxyResponseCommand.lo
CXX AbstractSingleDiskAdaptor.lo
CXX AdaptiveFileAllocationIterator.lo
CXX AdaptiveURISelector.lo
CXX AuthConfig.lo
CXX AuthConfigFactory.lo
CXX AutoSaveCommand.lo
CXX BackupIPv4ConnectCommand.lo
CXX base32.lo
CXX bitfield.lo
CXX BitfieldMan.lo
CXX BufferedFile.lo
CXX ByteArrayDiskWriter.lo
CXX CheckIntegrityCommand.lo
CXX CheckIntegrityDispatcherCommand.lo
CXX CheckIntegrityEntry.lo
CXX Checksum.lo
CXX ChecksumCheckIntegrityEntry.lo
CXX ChunkChecksum.lo
CXX ChunkedDecodingStreamFilter.lo
CXX ColorizedStream.lo
CXX Command.lo
CXX ConnectCommand.lo
CXX console.lo
CXX ConsoleStatCalc.lo
CXX ContentTypeRequestGroupCriteria.lo
CXX Context.lo
CXX ContextAttribute.lo
CXX Cookie.lo
CXX CookieStorage.lo
CXX cookie_helper.lo
CXX CreateRequestCommand.lo
CXX CUIDCounter.lo
CXX DefaultAuthResolver.lo
CXX DefaultBtProgressInfoFile.lo
CXX DefaultDiskWriter.lo
CXX DefaultDiskWriterFactory.lo
CXX DefaultPieceStorage.lo
DefaultBtProgressInfoFile.cc:267:24: error: use of undeclared identifier 'INFO_HASH_LENGTH'
267 | if (infoHashLength > INFO_HASH_LENGTH ||
| ^
DefaultBtProgressInfoFile.cc:268:26: error: use of undeclared identifier 'INFO_HASH_LENGTH'
268 | (infoHashLength != INFO_HASH_LENGTH && infoHashCheckEnabled)) {
| ^
DefaultBtProgressInfoFile.cc:272:31: error: use of undeclared identifier 'INFO_HASH_LENGTH'
272 | std::array<unsigned char, INFO_HASH_LENGTH> savedInfoHash;
| ^
3 errors generated.
make[3]: *** [Makefile:2638: DefaultBtProgressInfoFile.lo] Error 1
make[3]: *** Waiting for unfinished jobs....
make[3]: Leaving directory '/home/acer/aria2/aria2/src'
make[2]: *** [Makefile:2679: all-recursive] Error 1
make[2]: Leaving directory '/home/acer/aria2/aria2/src'
make[1]: *** [Makefile:557: all-recursive] Error 1
make[1]: Leaving directory '/home/acer/aria2/aria2'
make: *** [Makefile:468: all] Error 2