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Message-ID: <20240804142933.GW10433@brightrain.aerifal.cx>
Date: Sun, 4 Aug 2024 10:29:34 -0400
From: Rich Felker <dalias@...c.org>
To: contact@...ktivis.me
Cc: musl@...ts.openwall.com
Subject: Re: [PATCH 1/2] signal: add sig2str(3) from POSIX.1-2024
On Sun, Aug 04, 2024 at 02:41:44PM +0200, contact@...ktivis.me wrote:
> From: "Haelwenn (lanodan) Monnier" <contact@...ktivis.me>
>
> ---
> include/signal.h | 3 +++
> src/signal/sig2str.c | 59 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 62 insertions(+)
> create mode 100644 src/signal/sig2str.c
>
> diff --git a/include/signal.h b/include/signal.h
> index c347f861..217cfa08 100644
> --- a/include/signal.h
> +++ b/include/signal.h
> @@ -233,6 +233,9 @@ int pthread_kill(pthread_t, int);
> void psiginfo(const siginfo_t *, const char *);
> void psignal(int, const char *);
>
> +#define SIG2STR_MAX sizeof("RTMIN+32")
> +int sig2str(int signum, char *str);
> +
> #endif
>
> #if defined(_XOPEN_SOURCE) || defined(_BSD_SOURCE) || defined(_GNU_SOURCE)
> diff --git a/src/signal/sig2str.c b/src/signal/sig2str.c
> new file mode 100644
> index 00000000..85f64ec6
> --- /dev/null
> +++ b/src/signal/sig2str.c
> @@ -0,0 +1,59 @@
> +#include <signal.h>
> +#include <stdio.h>
> +#include <string.h>
> +
> +int sig2str(int signum, char *str)
> +{
> + const char *name = NULL;
> + switch(signum)
> + {
> + case SIGHUP: name = "HUP"; break;
> + case SIGINT: name = "INT"; break;
> + case SIGQUIT: name = "QUIT"; break;
> + case SIGILL: name = "ILL"; break;
> + case SIGTRAP: name = "TRAP"; break;
> + case SIGABRT: name = "ABRT"; break;
> + case SIGBUS: name = "BUS"; break;
> + case SIGFPE: name = "FPE"; break;
> + case SIGKILL: name = "KILL"; break;
> + case SIGUSR1: name = "USR1"; break;
> + case SIGSEGV: name = "SEGV"; break;
> + case SIGUSR2: name = "USR2"; break;
> + case SIGPIPE: name = "PIPE"; break;
> + case SIGALRM: name = "ALRM"; break;
> + case SIGTERM: name = "TERM"; break;
> + case SIGSTKFLT: name = "STKFLT"; break;
> + case SIGCHLD: name = "CHLD"; break;
> + case SIGCONT: name = "CONT"; break;
> + case SIGSTOP: name = "STOP"; break;
> + case SIGTSTP: name = "TSTP"; break;
> + case SIGTTIN: name = "TTIN"; break;
> + case SIGTTOU: name = "TTOU"; break;
> + case SIGURG: name = "URG"; break;
> + case SIGXCPU: name = "XCPU"; break;
> + case SIGXFSZ: name = "XFSZ"; break;
> + case SIGVTALRM: name = "VTALRM"; break;
> + case SIGPROF: name = "PROF"; break;
> + case SIGWINCH: name = "WINCH"; break;
> + case SIGIO: name = "IO"; break;
> + case SIGPWR: name = "PWR"; break;
> + case SIGSYS: name = "SYS"; break;
> + }
> +
> + // macros to functions can't be in switch-case
> + if(signum == SIGRTMIN) name = "RTMIN";
> + if(signum == SIGRTMAX) name = "RTMAX";
> +
> + if(SIGRTMIN+1 <= signum && signum <= SIGRTMAX-1)
> + {
> + if(snprintf(str, SIG2STR_MAX, "RTMIN+%i", signum-SIGRTMIN) < 0) return -1;
> +
> + return 0;
> + }
> +
> + if(name == NULL) return -1;
> +
> + strcpy(str, name);
> +
> + return 0;
> +}
> --
> 2.44.2
Could you do these with the approach of the existing strsignal.c? We
generally use that kind of single-concatenated-string table to avoid
ballooning numbers of dynamic relocations (and writable, nonshareable
memory) in each process shared libc.so is present in.
The sigmap[] machinery (only needed on one or two weird archs IIRC)
could be made external but hidden in a common file, so that it's not
duplicated again here.
Being that the standard signal names are bounded in length by 6, a
simple 2D array may be a better approach than having code to iterate
the concatenated multi-string like strsignal.c has. At most you waste
around 64 bytes this way, which is probably smaller than code, and
surely faster.
I see there's a little more logic needed for the realtime signals than
what strsignal.c has. I haven't yet read the spec but assuming the
above matches, I don't see a significantly lighter or simpler way than
what you'd doing. snprintf can't fail assuming valid format string and
non-overflowing-INT_MAX output, so error checking for it is not
needed.
Rich
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