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| author | Denys Vlasenko | 2017-07-28 15:28:33 +0200 |
|---|---|---|
| committer | Denys Vlasenko | 2017-07-28 15:28:33 +0200 |
| commit | 619d9b5e6848a72350126ea9c1e413fd133181e3 (patch) | |
| tree | 1fe4ab734bd3b917ec4e9ef35d2c1e700a850605 | |
| parent | 46f3f16b587ce781ab43a7b17698e1e565b2acf7 (diff) | |
| download | busybox-619d9b5e6848a72350126ea9c1e413fd133181e3.zip busybox-619d9b5e6848a72350126ea9c1e413fd133181e3.tar.gz | |
ash: less hackish implementation of evaltreenr()
Defining a function alias with __attribute__ ((alias("evaltree"),__noreturn__))
is not that usual, and clang had a bug which made it misunderstand
this construct.
Switch to:
ALWAYS_INLINE NORETURN evaltreenr() { evaltree(); unreachable(); }
Older gcc's do not know unreachable(), on them we pay the price of having
a few extra calls to abort():
function old new delta
evalsubshell 151 156 +5
evalpipe 357 362 +5
argstr 1141 1144 +3
On newer gcc, code size does not change.
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
| -rw-r--r-- | include/platform.h | 7 | ||||
| -rw-r--r-- | shell/ash.c | 20 |
2 files changed, 21 insertions, 6 deletions
diff --git a/include/platform.h b/include/platform.h index 8210e5c..ea49c7e 100644 --- a/include/platform.h +++ b/include/platform.h @@ -45,6 +45,13 @@ #define UNUSED_PARAM __attribute__ ((__unused__)) #define NORETURN __attribute__ ((__noreturn__)) + +#if __GNUC_PREREQ(4,5) +# define bb_unreachable(altcode) __builtin_unreachable() +#else +# define bb_unreachable(altcode) altcode +#endif + /* "The malloc attribute is used to tell the compiler that a function * may be treated as if any non-NULL pointer it returns cannot alias * any other pointer valid when the function returns. This will often diff --git a/shell/ash.c b/shell/ash.c index f74fbd7..1f5a8da 100644 --- a/shell/ash.c +++ b/shell/ash.c @@ -6137,6 +6137,19 @@ struct backcmd { /* result of evalbackcmd */ #define EV_TESTED 02 /* exit status is checked; ignore -e flag */ static int evaltree(union node *, int); +/* An evaltree() which is known to never return. + * Used to use an alias: + * static int evaltreenr(union node *, int) __attribute__((alias("evaltree"),__noreturn__)); + * but clang was reported to "transfer" noreturn-ness to evaltree() as well. + */ +static ALWAYS_INLINE NORETURN void +evaltreenr(union node *n, int flags) +{ + evaltree(n, flags); + bb_unreachable(abort()); + /* NOTREACHED */ +} + static void FAST_FUNC evalbackcmd(union node *n, struct backcmd *result) { @@ -6173,7 +6186,7 @@ evalbackcmd(union node *n, struct backcmd *result) */ eflag = 0; ifsfree(); - evaltree(n, EV_EXIT); /* actually evaltreenr... */ + evaltreenr(n, EV_EXIT); /* NOTREACHED */ } /* parent */ @@ -8796,11 +8809,6 @@ evaltree(union node *n, int flags) return exitstatus; } -#if !defined(__alpha__) || (defined(__GNUC__) && __GNUC__ >= 3) -static -#endif -int evaltreenr(union node *, int) __attribute__ ((alias("evaltree"),__noreturn__)); - static int skiploop(void) { |