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libbb: optionally honour libc provided SIGRTMIN/SIGRTMAX in get_signum()

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When an application documents that it responds such and such to
SIGRTMIN+n, that almost always means with respect to the libc-provided
SIGRTMIN. Hence I disagree with the "more correct" in commit
7b276fc175. In any case, this is rather unfortunate:

36
34

(the first shell is bash). We probably can't change default behaviour
after 7 years, but at least we can provide a config option.

We avoid a little code generation (repeated calls to
__libc_current_sigrtmin) by stashing SIGRTMIN/SIGRTMAX in local
variables, but it does cost ~50 bytes. The next patch serves as penance
for that.

Signed-off-by: Rasmus Villemoes <rasmus.villemoes@prevas.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Rasmus Villemoes 2018-09-12 16:06:36 +02:00 committed by Denys Vlasenko
parent 93ef5dd640
commit 571e525a14
1 changed files with 55 additions and 25 deletions
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80
libbb/u_signal_names.c
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@ -12,6 +12,18 @@
//config: help
//config: Support RTMIN[+n] and RTMAX[-n] signal names
//config: in kill, killall etc. This costs ~250 bytes.
//config:
//config:config FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
//config: bool "Use the definitions of SIGRTMIN/SIGRTMAX provided by libc"
//config: default y
//config: depends on FEATURE_RTMINMAX
//config: help
//config: Some C libraries reserve a few real-time signals for internal
//config: use, and adjust the values of SIGRTMIN/SIGRTMAX seen by
//config: applications accordingly. Saying yes here means that a signal
//config: name RTMIN+n will be interpreted according to the libc definition
//config: of SIGRTMIN, and not the raw definition provided by the kernel.
//config: This behavior matches "kill -l RTMIN+n" from bash.
#include "libbb.h"
@ -123,7 +135,7 @@ static const char signals[][7] ALIGN1 = {
#ifdef SIGSYS
[SIGSYS ] = "SYS",
#endif
#if ENABLE_FEATURE_RTMINMAX
#if ENABLE_FEATURE_RTMINMAX && !ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
# ifdef __SIGRTMIN
[__SIGRTMIN] = "RTMIN",
# endif
@ -168,36 +180,46 @@ int FAST_FUNC get_signum(const char *name)
# endif
#endif
#if ENABLE_FEATURE_RTMINMAX
# if defined(SIGRTMIN) && defined(SIGRTMAX)
/* libc may use some rt sigs for pthreads and therefore "remap" SIGRTMIN/MAX,
* but we want to use "raw" SIGRTMIN/MAX. Underscored names, if exist, provide
* them. If they don't exist, fall back to non-underscored ones: */
#if ENABLE_FEATURE_RTMINMAX && defined(SIGRTMIN) && defined(SIGRTMAX)
{
# if ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
/* Use the libc provided values. */
unsigned sigrtmin = SIGRTMIN;
unsigned sigrtmax = SIGRTMAX;
# else
/* Use the "raw" SIGRTMIN/MAX. Underscored names, if exist, provide
* them. If they don't exist, fall back to non-underscored ones: */
# if !defined(__SIGRTMIN)
# define __SIGRTMIN SIGRTMIN
# endif
# if !defined(__SIGRTMAX)
# define __SIGRTMAX SIGRTMAX
# endif
if (strncasecmp(name, "RTMIN", 5) == 0) {
if (!name[5])
return __SIGRTMIN;
if (name[5] == '+') {
i = bb_strtou(name + 6, NULL, 10);
if (!errno && i <= __SIGRTMAX - __SIGRTMIN)
return __SIGRTMIN + i;
}
}
else if (strncasecmp(name, "RTMAX", 5) == 0) {
if (!name[5])
return __SIGRTMAX;
if (name[5] == '-') {
i = bb_strtou(name + 6, NULL, 10);
if (!errno && i <= __SIGRTMAX - __SIGRTMIN)
return __SIGRTMAX - i;
}
}
# define sigrtmin __SIGRTMIN
# define sigrtmax __SIGRTMAX
# endif
if (strncasecmp(name, "RTMIN", 5) == 0) {
if (!name[5])
return sigrtmin;
if (name[5] == '+') {
i = bb_strtou(name + 6, NULL, 10);
if (!errno && i <= sigrtmax - sigrtmin)
return sigrtmin + i;
}
}
else if (strncasecmp(name, "RTMAX", 5) == 0) {
if (!name[5])
return sigrtmax;
if (name[5] == '-') {
i = bb_strtou(name + 6, NULL, 10);
if (!errno && i <= sigrtmax - sigrtmin)
return sigrtmax - i;
}
}
# undef sigrtmin
# undef sigrtmax
}
#endif
return -1;
@ -228,8 +250,16 @@ void FAST_FUNC print_signames(void)
printf("%2u) %s\n", signo, name);
}
#if ENABLE_FEATURE_RTMINMAX
# ifdef __SIGRTMAX
# if ENABLE_FEATURE_RTMINMAX_USE_LIBC_DEFINITIONS
# if defined(SIGRTMIN) && defined(SIGRTMAX)
printf("%2u) %s\n", SIGRTMIN, "RTMIN");
printf("%2u) %s\n", SIGRTMAX, "RTMAX");
# endif
# else
// __SIGRTMIN is included in signals[] array.
# ifdef __SIGRTMAX
printf("%2u) %s\n", __SIGRTMAX, "RTMAX");
# endif
# endif
#endif
}