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configure.ac: bashism: fix critical existence failure on systems with dash #517

Open eli-schwartz opened 6 months ago

eli-schwartz commented 6 months ago

Remove the consistent use of bashisms. An autoconf generated script is designed to work with POSIX sh, and contains a /bin/sh shebang. As a result, it cannot assume it will be run with bash, as it won't be.

The bashism in question is the double equals (==) operator for the test command. It is actually a bash-specific alias for the single equals operator. It behaves exactly the same, except more confusing. It contains no added functionality and no behavior changes, it is merely an additional alternate spelling. In exchange for doing nothing whatsoever, even in bash, it breaks muscle memory when writing POSIX sh scripts and tricks developers into writing the wrong thing.

It is terrible and should never be used under any circumstances. Ideally it would be removed altogether from GNU bash.

Fixes the following warnings when running configure:

./configure: 5011: test: x: unexpected operator
./configure: 5014: test: x: unexpected operator
./configure: 5017: test: x: unexpected operator
./configure: 8056: test: nox: unexpected operator
./configure: 8109: test: yesx: unexpected operator
./configure: 8120: test: 3: unexpected operator
./configure: 8144: test: unexpected operator
./configure: 9089: test: stdc++x: unexpected operator
./configure: 9937: test: 0: unexpected operator
./configure: 10084: test: 0: unexpected operator
./configure: 10207: test: 0: unexpected operator
./configure: 10283: test: 0: unexpected operator
./configure: 11363: test: x: unexpected operator
./configure: 11561: test: x: unexpected operator
./configure: 11634: test: xno: unexpected operator
./configure: 11663: test: xno: unexpected operator
./configure: 12490: test: 3: unexpected operator
./configure: 13150: test: no: unexpected operator
./configure: 13167: test: no: unexpected operator

And the following fatal errors when trying to compile, since the resulting conditionals failed to define $(PROTOCBIN):

make -j8
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/kismet.proto
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/http.proto
/bin/sh: 1: -I: not found
make: [Makefile:808: protobuf_cpp/kismet.pb.h] Error 127 (ignored)
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/datasource.proto
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/linuxbluetooth.proto
/bin/sh: 1: -I: not found
make: [Makefile:808: protobuf_cpp/http.pb.h] Error 127 (ignored)
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/eventbus.proto
/bin/sh: 1: -I: not found
make: [Makefile:808: protobuf_cpp/linuxbluetooth.pb.h] Error 127 (ignored)
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/kismet.proto
/bin/sh: 1: -I: not found
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/http.proto
/bin/sh: 1: -I: not found
/bin/sh: 1: -I: not found
make: [Makefile:808: protobuf_cpp/datasource.pb.h] Error 127 (ignored)
make: [Makefile:808: protobuf_cpp/eventbus.pb.h] Error 127 (ignored)
make: [Makefile:806: protobuf_cpp/kismet.pb.cc] Error 127 (ignored)
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/datasource.proto
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/linuxbluetooth.proto
cpp_out=./protobuf_cpp/ -I protobuf_definitions/ protobuf_definitions/eventbus.proto
/bin/sh: 1: -I: not found

For extra interest, the failing command begins with --flag i.e. a flag passed to protoc, which Make then interprets as "ignore errors for this command", which means output files are not created but the build then continues and produces significantly more confusing errors such as:

kis_external.h:51:10: fatal error: protobuf_cpp/kismet.pb.h: No such file or directory
eli-schwartz commented 4 months ago

Hi, I've rebased against git master so the changes still apply.

eli-schwartz commented 3 months ago

@dragorn is there anything outstanding I need to do to get this merged? The current state of affairs makes it quite challenging to build kismet on my system...