Expose inherit flag for process execution

Let the caller decide if stdout and stderr must be inherited on process
creation, i.e. if stdout and stderr of the child process should be
printed in the scrcpy console.

This allows to get output and errors for specific adb commands depending
on the context.

app/src/adb.c

@@ -132,8 +132,12 @@ adb_execute_p(const char *serial, const char *const adb_cmd[],
 
     memcpy(&argv[i], adb_cmd, len * sizeof(const char *));
     argv[len + i] = NULL;
+    unsigned inherit = SC_STDERR;
+    if (!pout) {
+        inherit |= SC_STDOUT;
+    }
     enum sc_process_result r =
-        sc_process_execute_p(argv, &pid, NULL, pout, NULL);
+        sc_process_execute_p(argv, &pid, inherit, NULL, pout, NULL);
     if (r != SC_PROCESS_SUCCESS) {
         show_adb_err_msg(r, argv);
         pid = SC_PROCESS_NONE;

app/src/sys/unix/process.c

@@ -11,8 +11,16 @@
 #include "util/log.h"
 
 enum sc_process_result
-sc_process_execute_p(const char *const argv[], sc_pid *pid,
+sc_process_execute_p(const char *const argv[], sc_pid *pid, unsigned inherit,
                      int *pin, int *pout, int *perr) {
+    bool inherit_stdout = inherit & SC_STDOUT;
+    bool inherit_stderr = inherit & SC_STDERR;
+
+    // If pout is defined, then inherit MUST NOT contain SC_STDOUT.
+    assert(!pout || !inherit_stdout);
+    // If perr is defined, then inherit MUST NOT contain SC_STDERR.
+    assert(!perr || !inherit_stderr);
+
     int in[2];
     int out[2];
     int err[2];
@@ -90,20 +98,31 @@ sc_process_execute_p(const char *const argv[], sc_pid *pid,
             }
             close(in[1]);
         }
+        // Do not close stdin in the child process, this makes adb fail on
+        // Linux
+
         if (pout) {
             if (out[1] != STDOUT_FILENO) {
                 dup2(out[1], STDOUT_FILENO);
                 close(out[1]);
             }
             close(out[0]);
+        } else if (!inherit_stdout) {
+            // Close stdout in the child process
+            close(STDOUT_FILENO);
         }
+
         if (perr) {
             if (err[1] != STDERR_FILENO) {
                 dup2(err[1], STDERR_FILENO);
                 close(err[1]);
             }
             close(err[0]);
+        } else if (!inherit_stderr) {
+            // Close stderr in the child process
+            close(STDERR_FILENO);
         }
+
         close(internal[0]);
         enum sc_process_result err;
         if (fcntl(internal[1], F_SETFD, FD_CLOEXEC) == 0) {

app/src/sys/win/process.c

@@ -27,12 +27,22 @@ build_cmd(char *cmd, size_t len, const char *const argv[]) {
 }
 
 enum sc_process_result
-sc_process_execute_p(const char *const argv[], HANDLE *handle,
+sc_process_execute_p(const char *const argv[], HANDLE *handle, unsigned inherit,
                      HANDLE *pin, HANDLE *pout, HANDLE *perr) {
-    enum sc_process_result ret = SC_PROCESS_ERROR_GENERIC;
+    bool inherit_stdout = inherit & SC_STDOUT;
+    bool inherit_stderr = inherit & SC_STDERR;
+
+    // If pout is defined, then inherit MUST NOT contain SC_STDOUT.
+    assert(!pout || !inherit_stdout);
+    // If perr is defined, then inherit MUST NOT contain SC_STDERR.
+    assert(!perr || !inherit_stderr);
 
     // Add 1 per non-NULL pointer
-    unsigned handle_count = !!pin + !!pout + !!perr;
+    unsigned handle_count = !!pin
+                          + (pout || inherit_stdout)
+                          + (perr || inherit_stderr);
+
+    enum sc_process_result ret = SC_PROCESS_ERROR_GENERIC;
 
     SECURITY_ATTRIBUTES sa;
     sa.nLength = sizeof(SECURITY_ATTRIBUTES);
@@ -80,20 +90,24 @@ sc_process_execute_p(const char *const argv[], HANDLE *handle,
     HANDLE handles[3];
 
     LPPROC_THREAD_ATTRIBUTE_LIST lpAttributeList = NULL;
-    if (handle_count) {
+    // Must be set even if handle_count == 0, so that stdin, stdout and stderr
-        si.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
+    // are NOT inherited in that case
+    si.StartupInfo.dwFlags = STARTF_USESTDHANDLES;
 
+    if (handle_count) {
         unsigned i = 0;
         if (pin) {
             si.StartupInfo.hStdInput = stdin_read_handle;
             handles[i++] = si.StartupInfo.hStdInput;
         }
-        if (pout) {
+        if (pout || inherit_stdout) {
-            si.StartupInfo.hStdOutput = stdout_write_handle;
+            si.StartupInfo.hStdOutput = pout ? stdout_write_handle
+                                             : GetStdHandle(STD_OUTPUT_HANDLE);
             handles[i++] = si.StartupInfo.hStdOutput;
         }
-        if (perr) {
+        if (perr || inherit_stderr) {
-            si.StartupInfo.hStdError = stderr_write_handle;
+            si.StartupInfo.hStdError = perr ? stderr_write_handle
+                                            : GetStdHandle(STD_ERROR_HANDLE);
             handles[i++] = si.StartupInfo.hStdError;
         }
 

app/src/util/process.c

@@ -5,8 +5,8 @@
 #include "log.h"
 
 enum sc_process_result
-sc_process_execute(const char *const argv[], sc_pid *pid) {
+sc_process_execute(const char *const argv[], sc_pid *pid, unsigned inherit) {
-    return sc_process_execute_p(argv, pid, NULL, NULL, NULL);
+    return sc_process_execute_p(argv, pid, inherit, NULL, NULL, NULL);
 }
 
 bool

app/src/util/process.h

@@ -67,20 +67,31 @@ enum sc_process_result {
     SC_PROCESS_ERROR_MISSING_BINARY,
 };
 
+#define SC_STDOUT (1 << 0)
+#define SC_STDERR (1 << 1)
+
 /**
  * Execute the command and write the process id to `pid`
+ *
+ * The parameter `inherit` is a OR of any of SC_STDOUT and SC_STDERR. It
+ * indicates if stdout and stderr must be inherited from the scrcpy process (in
+ * other words, if the process must output to the scrcpy console).
  */
 enum sc_process_result
-sc_process_execute(const char *const argv[], sc_pid *pid);
+sc_process_execute(const char *const argv[], sc_pid *pid, unsigned inherit);
 
 /**
  * Execute the command and write the process id to `pid`
  *
  * If not NULL, provide a pipe for stdin (`pin`), stdout (`pout`) and stderr
  * (`perr`).
+ *
+ * The parameter `inherit` has the same semantics as in `sc_process_execute()`.
+ * If `pout` is not NULL, then `inherit` MUST NOT contain SC_STDOUT.
+ * If `perr` is not NULL, then `inherit` MUST NOT contain SC_STDERR.
  */
 enum sc_process_result
-sc_process_execute_p(const char *const argv[], sc_pid *pid,
+sc_process_execute_p(const char *const argv[], sc_pid *pid, unsigned inherit,
                      sc_pipe *pin, sc_pipe *pout, sc_pipe *perr);
 
 /**