This is actually unnecessary as the call in question uses only fields
that have been set explicitly, but good practice regardless and it's
not like it's on a performance-critical path.
Reduce obfuscation of errno handling. There is only one purpose
non-local errno handling is needed for: Inside el_wgets(), several
functions call down indirectly to el_wgetc(), many of them via the
dispatch table. When el_wgetc() fails, it does properly report
failure, but then various cleanup is done which may clobber errno.
But when returning due to failure, el_wgets() wants to have errno
set to the reason of the original read failure, not to the reason
of some subsequent failure of some cleanup operation. So el_wgetc()
needs to save errno, and if it's non-zero, el_wgets() needs to
restore it on failure.
This core logic is currently obscured by the fact that el_errno
is set and inspected at some additional places where it isn't needed.
Besides, since el_wgetc() and and el_wgets() are both in read.c,
el_errno does not need to be in struct editline, it can and should
be local to read.c in struct el_read_t.
Let's look at what can be simplified.
1. keymacro_get() abuses el_errno instead of having a proper
error return code. Adding that error return code is easy
because node_trav() already detects the condition and an
adequate code is already defined. Returning it, testing
for it in read_getcmd(), and returning with error from there
removes the need to inspect el_errno from el_wgets() after
calling read_getcmd().
Note that resetting lastchar and cursor and clearing buffer[0]
is irrelevant. The code returns from el_wgets() right afterwards.
Outside el_wgets(), these variables are no longer relevant.
When el_wgets() is called the next time, it will call ch_reset()
anyway, resetting the two pointers. And as long as lastchar
points to the beginning of the buffer, the contents of the
buffer won't be used for anything.
2. read_getcmd() doesn't need to set el_errno again after el_wgetc()
failure since el_wgetc() already did so. While here, remove
the silly "if EOF or error" comments from the el_wgetc()
return value tests. It's a public interface documented in a
manual, so people working on the implementation can obviously
be expected to know how it works. It's a case of
count++; /* Increment count. */
3. In the two code paths of el_wgets() that lead up to "goto noedit",
there is no need to save the errno because nothing that might
change it happens before returning.
For clarity, since el_wgets() is the function restoring the errno,
also move initializing it to the same function.
Finally, note that restoring errno when the saved value is zero is
wrong. No library code is ever allowed to clear a previously set
value of errno. Only application programs are allowed to do that,
and even they usually don't need to do so, except when using certain
ill-designed interfaces like strtol(3).
I tested that the behaviour remains sane in the following cases,
all during execution of el_wgets(3) and with a signal handler
for USR1 installed without SA_RESTART.
* Enter some text and maybe move around a bit.
Then send a USR1 signal.
The signal gets processed, then read_char() resumes reading.
Send another USR1 signal.
Now el_wgets() sets errno=EINTR and returns -1.
* Press Ctrl-V to activate ed-quoted-insert.
Then send a USR1 signal.
The signal gets processed, then read_char() resumes reading.
Send another USR1 signal.
ed_quoted_insert() returns ed_end_of_file(), i.e. CC_EOF,
and el_wgets() returns 0.
* Press a key starting a keyboard macro.
Then send a USR1 signal.
The signal gets processed, then read_char() resumes reading.
Send another USR1 signal.
Now el_wgets() sets errno=EINTR and returns -1.
* Press : to enter builtin command mode.
Start typing a command.
Then send a USR1 signal.
The signal gets processed, then read_char() resumes reading.
Send another USR1 signal.
Now c_gets() returns -1, ed_command() beeps and returns CC_REFRESH,
and el_wgets() resumes operation as it should.
I also tested with "el_set(el, EL_EDITMODE, 0)", and it returns
the right value and sets errno correctly.
currently belonging to the chared module. The read module does so
from three of its functions, while no other module uses the macro
data, not even the chared module itself. That's quite logical
because macros are a feature of input handling, all of which is
done by the read module, and none by the chared module. So move
the data into the read modules's own opaque data structure, struct
el_read_t.
That simplifies internal interfaces in several respects: The
semi-public chared.h has one fewer struct, one fewer #define, and
one fewer member in struct el_chared_t; all three move to one single
C file, read.c, and are now module-local. And the internal interface
function ch_reset() needs one fewer argument, making the code of many
functions in various modules more readable.
The price is one additional internal interface function, read_end(),
10 lines long including comments, called publicly from exactly one
place: el_end() in el.c. That's hardly an increase in complexity
since most other modules already have their *_end() function, read.c
was the odd one out not having one.
From Ingo Schwarze
name, document the return values, expand the list of affected
functions, warn against using EL_GETCFN, and clarify some wording
and notation. (Ingo Schwarze)
Even though section "2.3.3 Information About the History List"
of the history(3) info(1) manual only says
-- Function: int where_history (void)
Returns the offset of the current history element.
which maybe isn't completely clear, a plausible implementation
is that the offset returned is the same offset that can be used
for history_set_pos(), i.e. that it is 0 for the oldest entry
and increases with time, and that's how the GNU implementation
behaves indeed.
The libedit implementation, on the other hand, returns 1 for the
newest entry and increases going back in time.
perspective of the dawn of time, so "next" means "newer" and "previous"
means "older". Libedit, by contrast, uses reverse chronology and
regards history from the perspective of the present, such that "next"
means "longer ago" and "previous" means "not so long ago".
The following patch fixes previous_history() and next_history()
as proposed by Bastian Maerkisch.
But there is a related problem demonstrated by Bastian's regression
tests that his patch did not fix: next_history() can advance not
only to the newest entry, but beyond it, which core libedit cannot
do. So that feature must be implemented locally in readline.c.
With that, the last of Bastians tests is fixed, test_movement_direction().
This patch also improves libedit documentation to more clearly state
what "previous" and "next" mean. GNU readline documentation is
just as unclear, but we can't easily fix that since libedit doesn't
include its own readline.3 manual.
(Ingo Schwarze)
implementation: libedit goes to the entry with the given number
stored in the HistEvent structure, while GNU subtracts history_base,
then advances that many entries from the oldest one. If entries were
removed in between, GNU advances further than libedit.
The call sequence H_CURR, H_DELDATA, H_CURR, H_NEXT_EVDATA looks
weird, as if part of that must somehow be redundant. But actually,
the user interface is so counter-intuitive that every single step
is really required.
- The first H_CURR is needed to be able to go back after an error.
- The H_DELDATA is needed to move the cursor. Even though it takes
a pointer to ev, that structure is not filled in when the call
succeeds. H_DELDATA only moves the cursor, it doesn't tell us
the new event number.
- Consequently, the second H_CURR is required to get ev.num filled
in. But it doesn't return the data because ev has no field for
that.
- So even though the cursor is already positioned correctly,
H_NEXT_EVDATA is needed as the final step merely to get the data.
(Ingo Schwarze)
- Put the data type el_rfunc_t into the public header <histedit.h>.
- Make el_read in struct editline an opaque pointer rather
than an embedded struct.
- Do not include "read.h" everywhere, but only in the two files
needing access to el_read, read.c and el.c.
- To functions that don't need more, pass the struct el_read_t *
rather than the full EditLine *.
- Of course, that means that read_init() can now fail from
memory exhaustion, but it's easy to clean up after that.
