envexec: add eligibility check for pipeMapping

issue: #98

.air.toml

@@ -2,7 +2,7 @@ root = "."
 
 [build]
 cmd = "go build -o ./tmp/go-judge ./cmd/go-judge"
-full_bin = "tmp/go-judge -enable-grpc -enable-debug -enable-metrics"
+full_bin = "tmp/go-judge -enable-grpc -enable-debug -enable-metrics -http-addr=:5050 -grpc-addr=:5051"
 
 include_ext = ["go"]
 exclude_dir = ["dist"]

README.cn.md

@@ -69,8 +69,8 @@ interface Cmd {
     args: string[]; // 程序命令行参数
     env?: string[]; // 程序环境变量
 
-    // 指定 标准输入、标准输出和标准错误的文件
-    files?: (LocalFile | MemoryFile | PreparedFile | Collector | StreamIn | StreamOut)[];
+    // 指定 标准输入、标准输出和标准错误的文件 (null 是为了 pipe 的使用情况准备的，而且必须被 pipeMapping 的 in / out 指定)
+    files?: (LocalFile | MemoryFile | PreparedFile | Collector | StreamIn | StreamOut | null)[];
     tty?: boolean; // 开启 TTY （需要保证标准输出和标准错误为同一文件）同时需要指定 TERM 环境变量 （例如 TERM=xterm）
 
     // 资源限制

README.md

@@ -69,8 +69,8 @@ interface Cmd {
     args: string[]; // command line argument
     env?: string[]; // environment
 
-    // specifies file input / pipe collector for program file descriptors
-    files?: (LocalFile | MemoryFile | PreparedFile | Collector | StreamIn | StreamOut)[];
+    // specifies file input / pipe collector for program file descriptors (null is reserved for pipe mapping and must be filled by in / out)
+    files?: (LocalFile | MemoryFile | PreparedFile | Collector | StreamIn | StreamOut ｜ null)[];
     tty?: boolean; // enables tty on the input and output pipes (should have just one input & one output)
     // Notice: must have TERM environment variables (e.g. TERM=xterm)
 

envexec/file_prepare.go

@@ -243,6 +243,12 @@ func prepareFds(r *Group, newStoreFile NewStoreFile) (f [][]*os.File, p [][]pipe
 
 	// prepare pipes
 	for _, p := range r.Pipes {
+		if files[p.Out.Index][p.Out.Fd] != nil {
+			return nil, nil, fmt.Errorf("pipe mapping to existing file descriptor: out %d/%d", p.Out.Index, p.Out.Fd)
+		}
+		if files[p.In.Index][p.In.Fd] != nil {
+			return nil, nil, fmt.Errorf("pipe mapping to existing file descriptor: in %d/%d", p.In.Index, p.In.Fd)
+		}
 		out, in, pc, err := pipe(p, newStoreFile)
 		if err != nil {
 			return nil, nil, err
@@ -254,6 +260,15 @@ func prepareFds(r *Group, newStoreFile NewStoreFile) (f [][]*os.File, p [][]pipe
 			pipeToCollect[p.In.Index] = append(pipeToCollect[p.In.Index], *pc)
 		}
 	}
+
+	// null check
+	for i, fds := range files {
+		for j, f := range fds {
+			if f == nil {
+				return nil, nil, fmt.Errorf("null passed to files for index/fd: %d/%d", i, j)
+			}
+		}
+	}
 	return files, pipeToCollect, nil
 }