The RubyVM uses C macro defines to feature detect whether
`backtrace(2)` support is available, and if so it includes C level backtraces
when the RubyVM itself crashes.
But on my machine, C level backtraces from `vm_dump.c` didn't work when
using a version of Ruby buillt on the machine, but worked fine when using a
version of Ruby built on another machine and copied to my machine.
The default autoconf test for backtraces uses a sigaltstack size that is
too small, so the SIGSEGV signal handler itself causes a SIGSEGV).
I noticed that signal.c uses a larger sigaltstack size:
https://github.com/ruby/ruby/blob/v2_6_5/signal.c#L568
The specific variables it looks at:
- `HAVE_BACKTRACE`
this is a macro defined by autoconf because there is a line in the
configure script like `AC_CHECK_FUNCS(backtrace)` (see the autoconf
docs for more).
- `BROKEN_BACKTRACE`
this comes from a custom program that Ruby's configure script runs to
attempt to figure out whether actually using backtrace(2) in a real
program works. You can see the autoconf program here.
<https://github.com/ruby/ruby/blob/v2_6_5/configure.ac#L2817-L2863>
It uses sigaltstack and SA_ONSTACK to create a seperate stack for
handling signals.
The problem was: SIGSTKSZ (which comes from a system header!) was not
suggesting a large enough stack size. When checking on an Ubuntu 16.04
box, we found that SIGSTKSZ was 8192 and MINSIGSTKSZ was 2048.
nobu-san reviewed,
https://github.com/ruby/irb/pull/106#pullrequestreview-423400033
> How about lexer = Ripper::Lexer.new(";\n#{code}", nil, 0)?
> Encoding pragma is effective only at the beginning.
> And the semicolon and newline will be skipped because the position is before
> the initial pos.
I employ the way.
Co-authored-by: Nobuyoshi Nakada <nobu@ruby-lang.org>
e593cc65b7
* fraction -> subsecond
for consistency with method name
* The sentence,
"A non-portable feature allows the offset to be negative on some systems.",
is removed.
Time before 1970 should work portably now.
If localtime() doesn't work before 1970,
Ruby should extrapolate it.
* Time::new -> Time.new
"::" for method call is not common notation now.
* Time#to_i truncates subsecond
* Time#to_f approximates a value in Time object
* Time#to_r
The sentence,
"You can use this method to convert _time_ to another Epoch.",
is removed.
It is not clear because no actual example of "another Epoch" is given.
* Time#usec truncates fraction of microseconds.
* Time#nsec truncates fraction of nanoseconds.
* describe Time#inspect shows subsecond since Ruby 2.7.0.
* RDoc: summary lists for options
* Enhanced RDoc for certain attributes and instance methods
* Enhanced RDoc for certain attributes and instance methods
* Enhanced RDoc for certain attributes and instance methods
* Enhanced RDoc for certain attributes and instance methods
72d8a25dc9
