spawn(): improve performance and simplify API

posix_spawn() is designed especially for this purpose, and thus it's
much more lightweight and efficient than manually fork/dup/exec-ing.

on my system, it improves the performance of spawn() by about 10x. given
that we make frequent calls to potentially multiple scripts, the
increased efficiency will add up overtime.

using posix_spawn() also simplifies the logic quite a bit, despite the
very verbose function names. however it does make cleanup a bit more
complicated.

this patch uses the linux kernel style cleanup strategy [0] (which I'm
personally not a huge fan of, but it fits this situation quite nicely)
with a "stack-like" unwinding via `goto`-s.

additionally simplify the spawn() API by taking in {read,write}fd
pointers and returning the pid instead of using some custom struct.

this coincidently also fixes #299

[0]: https://www.kernel.org/doc/html/v4.10/process/coding-style.html?highlight=goto#centralized-exiting-of-functions

1 files changed, 1 insertions, 12 deletions

diff --git a/nsxiv.h b/nsxiv.h
index 33a2bde..19e5399 100644
--- a/nsxiv.h
+++ b/nsxiv.h
@@ -326,17 +326,6 @@ typedef struct {
 	int stlen;
 } r_dir_t;
 
-typedef struct {
-	int readfd;
-	int writefd;
-	pid_t pid;
-} spawn_t;
-
-enum {
-	X_READ  = (1 << 0),
-	X_WRITE = (1 << 1)
-};
-
 extern const char *progname;
 
 void* emalloc(size_t);
@@ -349,7 +338,7 @@ int r_closedir(r_dir_t*);
 char* r_readdir(r_dir_t*, bool);
 int r_mkdir(char*);
 void construct_argv(char**, unsigned int, ...);
-spawn_t spawn(const char*, char *const [], unsigned int);
+pid_t spawn(int*, int*, char *const []);
 
 
 /* window.c */