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bfstd: New sysoption() macro to check for POSIX option runtime support
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POSIX allows optional features to be supported at compile time but not
necessarily at run time by defining _POSIX_OPTION to 0 and requiring
users to check sysconf(_SC_OPTION) > 0.  The new sysoption() macro
simplifies the check.

sighook() and bfs_spawn() now check for conditional runtime support for
the relevant POSIX options.
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@tavianator
tavianator committed Aug 10, 2024
1 parent baf9ee6 commit 1507cc2
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Showing 5 changed files with 84 additions and 39 deletions.
13 changes: 13 additions & 0 deletions src/bfstd.h
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Original file line number Diff line number Diff line change
Expand Up @@ -447,6 +447,19 @@ int xstrtofflags(const char **str, unsigned long long *set, unsigned long long *
*/
long xsysconf(int name);

/**
* Check for a POSIX option[1] at runtime.
*
* [1]: https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/V1_chap02.html#tag_02_01_06
*
* @param name
* The symbolic name of the POSIX option (e.g. SPAWN).
* @return
* The value of the option, either -1 or a date like 202405.
*/
#define sysoption(name) \
(_POSIX_##name == 0 ? xsysconf(_SC_##name) : _POSIX_##name)

#include <wchar.h>

/**
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11 changes: 7 additions & 4 deletions src/eval.c
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Original file line number Diff line number Diff line change
Expand Up @@ -1018,12 +1018,15 @@ bool eval_xtype(const struct bfs_expr *expr, struct bfs_eval *state) {
* clock_gettime() wrapper.
*/
static int eval_gettime(struct bfs_eval *state, struct timespec *ts) {
#if _POSIX_MONOTONIC_CLOCK > 0
int ret = clock_gettime(CLOCK_MONOTONIC, ts);
#else
int ret = clock_gettime(CLOCK_REALTIME, ts);
clockid_t clock = CLOCK_REALTIME;

#if defined(_POSIX_MONOTONIC_CLOCK) && _POSIX_MONOTONIC_CLOCK >= 0
if (sysoption(MONOTONIC_CLOCK) > 0) {
clock = CLOCK_MONOTONIC;
}
#endif

int ret = clock_gettime(clock, ts);
if (ret != 0) {
bfs_warning(state->ctx, "%pP: clock_gettime(): %s.\n", state->ftwbuf, errstr());
}
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24 changes: 17 additions & 7 deletions src/sighook.c
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Original file line number Diff line number Diff line change
Expand Up @@ -29,7 +29,13 @@
#include <stdlib.h>
#include <unistd.h>

#if _POSIX_SEMAPHORES > 0
#ifdef _POSIX_SEMAPHORES
# define BFS_POSIX_SEMAPHORES _POSIX_SEMAPHORES
#else
# define BFS_POSIX_SEMAPHORES (-1)
#endif

#if BFS_POSIX_SEMAPHORES >= 0
# include <semaphore.h>
#endif

Expand All @@ -42,7 +48,7 @@ struct arc {
/** The reference itself. */
void *ptr;

#if _POSIX_SEMAPHORES > 0
#if BFS_POSIX_SEMAPHORES >= 0
/** A semaphore for arc_wake(). */
sem_t sem;
/** sem_init() result. */
Expand All @@ -57,8 +63,12 @@ static void arc_init(struct arc *arc) {
atomic_init(&arc->refs, 0);
arc->ptr = NULL;

#if _POSIX_SEMAPHORES > 0
arc->sem_status = sem_init(&arc->sem, false, 0);
#if BFS_POSIX_SEMAPHORES >= 0
if (sysoption(SEMAPHORES) > 0) {
arc->sem_status = sem_init(&arc->sem, false, 0);
} else {
arc->sem_status = -1;
}
#endif
}

Expand Down Expand Up @@ -93,7 +103,7 @@ static void arc_put(struct arc *arc) {
size_t refs = fetch_sub(&arc->refs, 1, release);

if (refs == 1) {
#if _POSIX_SEMAPHORES > 0
#if BFS_POSIX_SEMAPHORES >= 0
if (arc->sem_status == 0 && sem_post(&arc->sem) != 0) {
abort();
}
Expand All @@ -103,7 +113,7 @@ static void arc_put(struct arc *arc) {

/** Wait on the semaphore. */
static int arc_sem_wait(struct arc *arc) {
#if _POSIX_SEMAPHORES > 0
#if BFS_POSIX_SEMAPHORES >= 0
if (arc->sem_status == 0) {
while (sem_wait(&arc->sem) != 0) {
bfs_everify(errno == EINTR, "sem_wait()");
Expand Down Expand Up @@ -146,7 +156,7 @@ done:;
static void arc_destroy(struct arc *arc) {
bfs_assert(arc_refs(arc) == 0);

#if _POSIX_SEMAPHORES > 0
#if BFS_POSIX_SEMAPHORES >= 0
if (arc->sem_status == 0) {
bfs_everify(sem_destroy(&arc->sem) == 0, "sem_destroy()");
}
Expand Down
65 changes: 39 additions & 26 deletions src/xspawn.c
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Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,7 @@
# include <paths.h>
#endif

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
# include <spawn.h>
#endif

Expand Down Expand Up @@ -70,29 +70,42 @@ int bfs_spawn_init(struct bfs_spawn *ctx) {
ctx->flags = 0;
SLIST_INIT(ctx);

#if _POSIX_SPAWN > 0
ctx->flags |= BFS_SPAWN_USE_POSIX;
#if BFS_POSIX_SPAWN >= 0
if (sysoption(SPAWN) > 0) {
ctx->flags |= BFS_SPAWN_USE_POSIX;

errno = posix_spawn_file_actions_init(&ctx->actions);
if (errno != 0) {
return -1;
}
errno = posix_spawn_file_actions_init(&ctx->actions);
if (errno != 0) {
return -1;
}

errno = posix_spawnattr_init(&ctx->attr);
if (errno != 0) {
posix_spawn_file_actions_destroy(&ctx->actions);
return -1;
errno = posix_spawnattr_init(&ctx->attr);
if (errno != 0) {
posix_spawn_file_actions_destroy(&ctx->actions);
return -1;
}
}
#endif

return 0;
}

int bfs_spawn_destroy(struct bfs_spawn *ctx) {
#if _POSIX_SPAWN > 0
posix_spawnattr_destroy(&ctx->attr);
posix_spawn_file_actions_destroy(&ctx->actions);
/**
* Clear the BFS_SPAWN_USE_POSIX flag and free the attributes.
*/
static void bfs_spawn_clear_posix(struct bfs_spawn *ctx) {
if (ctx->flags & BFS_SPAWN_USE_POSIX) {
ctx->flags &= ~BFS_SPAWN_USE_POSIX;

#if BFS_POSIX_SPAWN >= 0
posix_spawnattr_destroy(&ctx->attr);
posix_spawn_file_actions_destroy(&ctx->actions);
#endif
}
}

int bfs_spawn_destroy(struct bfs_spawn *ctx) {
bfs_spawn_clear_posix(ctx);

for_slist (struct bfs_spawn_action, action, ctx) {
free(action);
Expand All @@ -101,7 +114,7 @@ int bfs_spawn_destroy(struct bfs_spawn *ctx) {
return 0;
}

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
/** Set some posix_spawnattr flags. */
_maybe_unused
static int bfs_spawn_addflags(struct bfs_spawn *ctx, short flags) {
Expand All @@ -121,7 +134,7 @@ static int bfs_spawn_addflags(struct bfs_spawn *ctx, short flags) {

return 0;
}
#endif // _POSIX_SPAWN > 0
#endif

/** Allocate a spawn action. */
static struct bfs_spawn_action *bfs_spawn_action(enum bfs_spawn_op op) {
Expand All @@ -143,7 +156,7 @@ int bfs_spawn_addopen(struct bfs_spawn *ctx, int fd, const char *path, int flags
return -1;
}

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
if (ctx->flags & BFS_SPAWN_USE_POSIX) {
errno = posix_spawn_file_actions_addopen(&ctx->actions, fd, path, flags, mode);
if (errno != 0) {
Expand All @@ -167,7 +180,7 @@ int bfs_spawn_addclose(struct bfs_spawn *ctx, int fd) {
return -1;
}

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
if (ctx->flags & BFS_SPAWN_USE_POSIX) {
errno = posix_spawn_file_actions_addclose(&ctx->actions, fd);
if (errno != 0) {
Expand All @@ -188,7 +201,7 @@ int bfs_spawn_adddup2(struct bfs_spawn *ctx, int oldfd, int newfd) {
return -1;
}

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
if (ctx->flags & BFS_SPAWN_USE_POSIX) {
errno = posix_spawn_file_actions_adddup2(&ctx->actions, oldfd, newfd);
if (errno != 0) {
Expand Down Expand Up @@ -228,7 +241,7 @@ int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) {
# define BFS_POSIX_SPAWN_ADDFCHDIR posix_spawn_file_actions_addfchdir_np
#endif

#if _POSIX_SPAWN > 0 && defined(BFS_POSIX_SPAWN_ADDFCHDIR)
#if BFS_POSIX_SPAWN >= 0 && defined(BFS_POSIX_SPAWN_ADDFCHDIR)
if (ctx->flags & BFS_SPAWN_USE_POSIX) {
errno = BFS_POSIX_SPAWN_ADDFCHDIR(&ctx->actions, fd);
if (errno != 0) {
Expand All @@ -237,7 +250,7 @@ int bfs_spawn_addfchdir(struct bfs_spawn *ctx, int fd) {
}
}
#else
ctx->flags &= ~BFS_SPAWN_USE_POSIX;
bfs_spawn_clear_posix(ctx);
#endif

action->in_fd = fd;
Expand All @@ -261,7 +274,7 @@ int bfs_spawn_setrlimit(struct bfs_spawn *ctx, int resource, const struct rlimit
goto fail;
}
#else
ctx->flags &= ~BFS_SPAWN_USE_POSIX;
bfs_spawn_clear_posix(ctx);
#endif

action->resource = resource;
Expand Down Expand Up @@ -482,7 +495,7 @@ static int bfs_resolve_early(struct bfs_resolver *res, const char *exe, const st
return -1;
}

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0

/** bfs_spawn() implementation using posix_spawn(). */
static pid_t bfs_posix_spawn(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) {
Expand Down Expand Up @@ -516,7 +529,7 @@ static bool bfs_use_posix_spawn(const struct bfs_resolver *res, const struct bfs
return true;
}

#endif // _POSIX_SPAWN > 0
#endif // BFS_POSIX_SPAWN >= 0

/** Actually exec() the new process. */
_noreturn
Expand Down Expand Up @@ -653,7 +666,7 @@ static pid_t bfs_fork_spawn(struct bfs_resolver *res, const struct bfs_spawn *ct

/** Call the right bfs_spawn() implementation. */
static pid_t bfs_spawn_impl(struct bfs_resolver *res, const struct bfs_spawn *ctx, char **argv, char **envp) {
#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
if (bfs_use_posix_spawn(res, ctx)) {
return bfs_posix_spawn(res, ctx, argv, envp);
}
Expand Down
10 changes: 8 additions & 2 deletions src/xspawn.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,7 +13,13 @@
#include <sys/types.h>
#include <unistd.h>

#if _POSIX_SPAWN > 0
#ifdef _POSIX_SPAWN
# define BFS_POSIX_SPAWN _POSIX_SPAWN
#else
# define BFS_POSIX_SPAWN (-1)
#endif

#if BFS_POSIX_SPAWN >= 0
# include <spawn.h>
#endif

Expand All @@ -38,7 +44,7 @@ struct bfs_spawn {
struct bfs_spawn_action *head;
struct bfs_spawn_action **tail;

#if _POSIX_SPAWN > 0
#if BFS_POSIX_SPAWN >= 0
/** posix_spawn() context, for when we can use it. */
posix_spawn_file_actions_t actions;
posix_spawnattr_t attr;
Expand Down

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