Make nxlink stdio more flexible, see details:

- Added nxlinkConnectToHost with separate flags for redirecting stdout/err
- Added nxlinkStdioForDebug, which only redirects stderr
- (nxlinkStdio now just calls nxlinkConnectToHost)

nx/include/switch/runtime/nxlink.h

@@ -5,6 +5,7 @@
  * @copyright libnx Authors
  */
 #pragma once
+#include "../types.h"
 
 struct in_addr;
 
@@ -15,8 +16,20 @@ extern struct in_addr __nxlink_host;
 #define NXLINK_CLIENT_PORT 28771 ///< nxlink TCP client port
 
 /**
- * @brief Sets up stdout/stderr redirection to the nxlink host.
+ * @brief Connects to the nxlink host, setting up an output stream.
+ * @param[in] redirStdout Whether to redirect stdout to nxlink output.
+ * @param[in] redirStderr Whether to redirect stderr to nxlink output.
  * @return Socket fd on success, negative number on failure.
  * @note The socket should be closed with close() during application cleanup.
  */
-int nxlinkStdio(void);
+int nxlinkConnectToHost(bool redirStdout, bool redirStderr);
+
+/// Same as \ref nxlinkConnectToHost but redirecting both stdout/stderr.
+NX_INLINE int nxlinkStdio(void) {
+    return nxlinkConnectToHost(true, true);
+}
+
+/// Same as \ref nxlinkConnectToHost but redirecting only stderr.
+NX_INLINE int nxlinkStdioForDebug(void) {
+    return nxlinkConnectToHost(false, true);
+}

nx/source/runtime/nxlink_stdio.c

@@ -9,7 +9,7 @@
 
 static int sock = -1;
 
-int nxlinkStdio(void)
+int nxlinkConnectToHost(bool redirStdout, bool redirStderr)
 {
     int ret = -1;
     struct sockaddr_in srv_addr;
@@ -30,12 +30,17 @@ int nxlinkStdio(void)
         return -1;
     }
 
-    // redirect stdout
-    fflush(stdout);
-    dup2(sock, STDOUT_FILENO);
-    // redirect stderr
-    fflush(stderr);
-    dup2(sock, STDERR_FILENO);
+    if (redirStdout) {
+        // redirect stdout
+        fflush(stdout);
+        dup2(sock, STDOUT_FILENO);
+    }
+
+    if (redirStderr) {
+        // redirect stderr
+        fflush(stderr);
+        dup2(sock, STDERR_FILENO);
+    }
 
     return sock;
 }