Changes from v4:
- Applied Simon's patch to refactor the unittest. Thanks, Simon!
This patch implements the ability to set/unset environment variables
on the remote target, mimicking what GDB already offers to the user.
There are two features present here: user-set and user-unset
environment variables.
User-set environment variables are only the variables that are
explicitly set by the user, using the 'set environment' command. This
means that variables that were already present in the environment when
starting GDB/GDBserver are not transmitted/considered by this feature.
User-unset environment variables are variables that are explicitly
unset by the user, using the 'unset environment' command.
The idea behind this patch is to store user-set and user-unset
environment variables in two separate sets, both part of gdb_environ.
Then, when extended_remote_create_inferior is preparing to start the
inferior, it will iterate over the two sets and set/unset variables
accordingly. Three new packets are introduced:
- QEnvironmentHexEncoded, which is used to set environment variables,
and contains an hex-encoded string in the format "VAR=VALUE" (VALUE
can be empty if the user set a variable with a null value, by doing
'set environment VAR=').
- QEnvironmentUnset, which is used to unset environment variables, and
contains an hex-encoded string in the format "VAR".
- QEnvironmentReset, which is always the first packet to be
transmitted, and is used to reset the environment, i.e., discard any
changes made by the user on previous runs.
The QEnvironmentHexEncoded packet is inspired on LLDB's extensions to
the RSP. Details about it can be seen here:
<https://raw.githubusercontent.com/llvm-mirror/lldb/master/docs/lldb-gdb-remote.txt>
I decided not to implement the QEnvironment packet because it is
considered deprecated by LLDB. This packet, on LLDB, serves the same
purpose of QEnvironmentHexEncoded, but sends the information using a
plain text, non-hex-encoded string.
The other two packets are new.
This patch also includes updates to the documentation, testsuite, and
unit tests, without introducing regressions.