For some reason, we have two places where a variable can be read-only:
- By key in env.cpp:is_read_only(), which is checked via set*
- By flag on the actual env_var_t, which is checked e.g. in
parse_execution
The latter didn't happen for non-electric variables like hostname,
because they used the default constructor, because they were
constructed via operator[] (or some such C++-iness).
This caused for-loops to crash on an assert if they used a
non-electric read-only var like $hostname or $SHLVL.
Instead, we explicitly set the flag.
We might want to remove one of the two read-only checks, or something?
Fixes#5548.
Our is_hex_digit() was redundant, we can just use iswxdigit; the libc
implementation is a more efficient table lookup anyhow.
Do is_octal_digit() in terms of iswdigit instead of using wcschr.
This requires threading environment_t through many places, such as completions
and history. We introduce null_environment_t for when the environment isn't
important.
`xlocale.h` is not available on Linux, so we can't just universally
include it.
`HAVE_XLOCALE_H` was already being tested/set in the CMake script as a
possible requirement for `wcstod_l` support, this just adds it to
`config_cmake_h.in` and uses it in `wutil.h` to gate the include.
Removes the dependency on the current user's home directory, instead
overriding it to be within the current hierarchy.
Fixes the tests on Debian buildd, where the home directory is
deliberately unwriteable to pick up errors in builds.
Using `setlocale` is both not thread-safe and not correct, as
a) The global locale is usually stored in static storage, so
simultaneous calls to `setlocale` can result in corruption, and
b) `setlocale` changes the locale for the entire application, not
just the calling thread. This means that even if we wrapped the
`wcstod_l` in a mutex to prevent the previous point, the results
would still be incorrect because this would incorrectly influence the
results of locale-aware functions executed in other threads while
this thread is executing.
The previous comment mentioned that `uselocale` hadn't worked. I'm not
sure what the failing implementation looked like, but `uselocale` can be
tricky. The committed implementation passes the tests for me under Linux
and FreeBSD.
This was the actual issue leading to memory corruption under FreeBSD in
issue #5453, worked around by correcting the detection of `wcstod_l` so
that our version of the function is not called at all.
If we are 100% certain that `wcstod_l` does not exist, then then the
existing code is fine. But given that our checks have failed seperately
on two different platforms already (FreeBSD and Cygwin/newlib), it's a
good precaution to take.
