| Message ID | 20201223210257.78887-1-june@causal.agency (mailing list archive) |
|---|---|
| State | Rejected |
| Delegated to: | Herbert Xu |
| Headers | show |
| Series | [v2] Cache the expanded prompt for editline | expand |
C. McEnroe <june@causal.agency> wrote: > Previously, the prompt would be expanded every time editline called the > getprompt callback. I think the code may have been written assuming that > editline only calls getprompt once per prompt, but it may actually call > it many times, for instance every time you type backspace. This results > not only in slower editing from expanding complex prompts repeatedly, it > also consumes more and more stack memory each time getprompt is called. > This can be seen by setting PS1 to some command substitution, typing > many characters at the prompt, then holding backspace and observing > memory usage. Thankfully all this stack memory is freed between prompts > by the stackmark calls around el_gets. > > This change causes prompt expansion to always happen in the setprompt > call, as it would when editline is disabled, and a cached copy of the > prompt is saved for getprompt to return every time editline calls it. > Since getprompt is no longer doing expansion, the stackmark calls > surrounding el_gets can be removed. > --- > > v2: Missed adding breaks when replacing returns with assignments. What if someone actually wanted the prompt to change? Cheers,
> On Jan 13, 2021, at 01:18, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > What if someone actually wanted the prompt to change? It seems unlikely given the lack of consistency of when libedit calls the prompt callback. I only noticed it was happening when I patched in support for EL_RPROMPT (right-aligned prompts), which when active causes libedit to call the prompt callback on *every* keypress. It seemed not to happen with only a regular prompt and it took some experimenting to notice typing backspaces causes it. The behaviour is completely undocumented in libedit. Anecdotally, typing at the prompt becomes painful when it is expanded over and over and does anything non-trivial, even just a command substitution that runs no external commands.
On Thu, Jan 14, 2021 at 10:43:21AM -0500, June Bug wrote: > > It seems unlikely given the lack of consistency of when libedit > calls the prompt callback. I only noticed it was happening when I > patched in support for EL_RPROMPT (right-aligned prompts), which > when active causes libedit to call the prompt callback on *every* > keypress. It seemed not to happen with only a regular prompt and > it took some experimenting to notice typing backspaces causes it. > The behaviour is completely undocumented in libedit. > > Anecdotally, typing at the prompt becomes painful when it is expanded > over and over and does anything non-trivial, even just a command > substitution that runs no external commands. OK, in that case I think it's best to fix this in libedit instead. Thanks,
> On Jan 14, 2021, at 15:12, Herbert Xu <herbert@gondor.apana.org.au> wrote: > > OK, in that case I think it's best to fix this in libedit instead. Huh? There’s no issue in libedit, only unclear documentation. The application is the right place to store the prompt: it can be in a static buffer, or a constant string, in which case libedit has no need to save its own copy.
diff --git a/src/input.c b/src/input.c index 17544e7..4167bd1 100644 --- a/src/input.c +++ b/src/input.c @@ -152,12 +152,8 @@ retry: static const char *rl_cp; static int el_len; - if (rl_cp == NULL) { - struct stackmark smark; - pushstackmark(&smark, stackblocksize()); + if (rl_cp == NULL) rl_cp = el_gets(el, &el_len); - popstackmark(&smark); - } if (rl_cp == NULL) nr = 0; else { diff --git a/src/parser.c b/src/parser.c index a47022e..270a01d 100644 --- a/src/parser.c +++ b/src/parser.c @@ -107,6 +107,9 @@ struct heredoc *heredoc; int quoteflag; /* set if (part of) last token was quoted */ +static char *promptcache; + + STATIC union node *list(int); STATIC union node *andor(void); STATIC union node *pipeline(void); @@ -1541,27 +1544,6 @@ synerror(const char *msg) /* NOTREACHED */ } -STATIC void -setprompt(int which) -{ - struct stackmark smark; - int show; - - needprompt = 0; - whichprompt = which; - -#ifdef SMALL - show = 1; -#else - show = !el; -#endif - if (show) { - pushstackmark(&smark, stackblocksize()); - out2str(getprompt(NULL)); - popstackmark(&smark); - } -} - const char * expandstr(const char *ps) { @@ -1611,22 +1593,25 @@ out: return result; } -/* - * called by editline -- any expansions to the prompt - * should be added here. - */ -const char * -getprompt(void *unused) +STATIC void +setprompt(int which) { + struct stackmark smark; const char *prompt; + int show; + + needprompt = 0; + whichprompt = which; switch (whichprompt) { default: #ifdef DEBUG - return "<internal prompt error>"; + prompt = "<internal prompt error>"; + break; #endif case 0: - return nullstr; + prompt = nullstr; + break; case 1: prompt = ps1val(); break; @@ -1635,7 +1620,28 @@ getprompt(void *unused) break; } - return expandstr(prompt); +#ifdef SMALL + show = 1; +#else + show = !el; +#endif + pushstackmark(&smark, stackblocksize()); + if (show) { + out2str(expandstr(prompt)); + } else { + free(promptcache); + promptcache = savestr(expandstr(prompt)); + } + popstackmark(&smark); +} + +/* + * called by editline -- return the cached prompt expansion. + */ +const char * +getprompt(void *unused) +{ + return promptcache; } const char *const *