Make execvp work with zero allocations.

	This fixes a bug when exec'ing from forked
	process in a program that uses threads.

	The allocator from another thread can be
	holding the lock at fork, so when we fork
	it's possible that there's nobody left to
	unlock, and we deeadlock.

1 files changed, 26 insertions, 17 deletions

diff --git a/lib/std/execvp.myr b/lib/std/execvp.myr
index f6696e3..c24ea47 100644
--- a/lib/std/execvp.myr
+++ b/lib/std/execvp.myr
@@ -4,7 +4,6 @@ use "errno"
 use "fmt"
 use "option"
 use "strfind"
-use "strsplit"
 use "syswrap"
 
 pkg std = 
@@ -13,46 +12,56 @@ pkg std =
 ;;
 
 const execvp = {cmd, args
-	var paths, binpath
+	var i, j, paths, binpath
 	var buf : byte[512]
 
 	match strfind(cmd, "/")
 	| `Some _:
 		-> execv(cmd, args)
 	| `None:
-		paths = getpaths()
-		for p : paths
-			binpath = bfmt(buf[:], "{}/{}", p, cmd)
+		i = 0
+		j = 0
+		paths = std.getenvv("PATH", "/usr/local/bin:/bin:/usr/bin")
+		while j < paths.len
+			(i, j) = nextpath(paths, j)
+			binpath = bfmt(buf[:], "{}/{}", paths[i:j], cmd)
 			execv(binpath, args)
 		;;
-		slfree(paths)
 	;;
 	-> -1
 }
 
 const execvpe = {cmd, args, env
-	var paths, binpath
+	var i, j, paths, binpath
 	var buf : byte[512]
 
 	match strfind(cmd, "/")
 	| `Some _:
 		-> execve(cmd, args, env)
 	| `None:
-		paths = getpaths()
-		for p : paths
-			binpath = bfmt(buf[:], "{}/{}", p, cmd)
+		i = 0
+		j = 0
+		paths = std.getenvv("PATH", "/usr/local/bin:/bin:/usr/bin")
+		while j < paths.len
+			(i, j) = nextpath(paths, j)
+			binpath = bfmt(buf[:], "{}/{}", paths[i:j], cmd)
 			execve(binpath, args, env)
 		;;
-		slfree(paths)
 	;;
 	-> -1
 }
 
-const getpaths = {
-	var path
-	match getenv("PATH")
-	| `Some p:	path = p
-	| `None:	path = "/usr/local/bin:/bin:/usr/bin"
+const nextpath = {p, start
+	var i, j
+
+	i = start
+	while i < p.len && p[i] == (':' : byte)
+		i++
+	;;
+	j = i
+	while j < p.len && p[j] != (':' : byte)
+		j++
 	;;
-	-> strsplit(path, ":")
+	-> (i, j)
 }
+