Use the newer "legacy" way of determining whether a file descriptor is
using proto2 or proto3 syntax on protobuf >= 23.0.
Based on
66574f3fd8
but continues to support older versions of protobuf.
Unfortunately, since this is a "deprecated", "legacy" API it'll probably
disappear in about five seconds.
According to the protobuf migration guide as of June 2023 [0], protobuf
22.0 (aka 4.22.0) took a dependency on something called "abseil" and as
a result the "stubs" have been removed. This apparently caused all the
uses of GOOGLE_* identifiers in protoc-c to fail when building against
newer versions of protobuf.
This commit introduces compatibility definitions when building against
protobuf >= 4.22.0 so that protobuf-c can build against older and newer
versions of protobuf.
[0] https://web.archive.org/web/20230611151200/https://protobuf.dev/support/migration/#abseil
The protobuf common.h header currently has a "using std::string;"
statement that pulls std::string into the google::protobuf namespace:
ce66f6047d/src/google/protobuf/stubs/common.h (L195)
I plan to delete that line soon. To keep protobuf-c working, this commit
updates the generator to fully qualify std::string.
This is a first cut at adding proto3 support.
As far as I understand protobuf-c already has pretty much everything
needed once it is built using a new version of protobuf itself.
The only missing thing is that in proto3 all fields are optional and
having to manually set has_foo is inconvenient.
This patch special cases the proto3 syntax files so that structs for the
bytes, enum and primitive fields do not emit the has_ field.
It also adds PROTOBUF_C_LABEL_NONE to the label enum that is used for
proto3 fields. When a fields has this label, the quantifier is not
consulted and instead the field is packed/unpacked depending on
whether it has a value different from NULL/0.
per https://code.google.com/p/protobuf/source/detail?r=50, the license
on google-originated protobuf code was switched from Apache-2.0 to
BSD-3-Clause (so-called "New BSD" license). update any of the google
license statements to use this new license.
per email with dave, drop the third clause on his BSD-3-Clause license,
so this now becomes BSD-2-Clause.
make sure to use consistent indentation and wrapping throughout.
