Processing (Linux): interrupt poll & read syscalls when the child process is exited

Fix fastfetch-cli#1418

Author: CarterLi

src/common/init.c

@@ -76,19 +76,21 @@ static void resetConsole(void)
 }
 
 #ifdef _WIN32
-BOOL WINAPI consoleHandler(DWORD signal)
+BOOL WINAPI consoleHandler(FF_MAYBE_UNUSED DWORD signal)
 {
-    FF_UNUSED(signal);
     resetConsole();
     exit(0);
 }
 #else
-static void exitSignalHandler(int signal)
+static void exitSignalHandler(FF_MAYBE_UNUSED int signal)
 {
-    FF_UNUSED(signal);
     resetConsole();
     exit(0);
 }
+static void chldSignalHandler(FF_MAYBE_UNUSED int signal)
+{
+    // empty; used to interrupt the poll and read syscalls
+}
 #endif
 
 void ffStart(void)
@@ -118,6 +120,7 @@ void ffStart(void)
     sigaction(SIGINT, &action, NULL);
     sigaction(SIGTERM, &action, NULL);
     sigaction(SIGQUIT, &action, NULL);
+    sigaction(SIGCHLD, &(struct sigaction) { .sa_handler = chldSignalHandler }, NULL);
     #endif
 
     //reset everything to default before we start printing

src/common/processing_linux.c

@@ -1,7 +1,6 @@
 #include "fastfetch.h"
 #include "common/processing.h"
 #include "common/io/io.h"
-#include "common/time.h"
 #include "util/stringUtils.h"
 #include "util/mallocHelper.h"
 
@@ -90,6 +89,16 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
                 waitpid(childPid, NULL, 0);
                 return "poll(&pollfd, 1, timeout) timeout (try increasing --processing-timeout)";
             }
+            else if (errno == EINTR)
+            {
+                // The child process has been terminated. See `chldSignalHandler` in `common/init.c`
+                if (waitpid(childPid, NULL, WNOHANG) == childPid)
+                {
+                    // Read remaining data from the pipe
+                    fcntl(childPipeFd, F_SETFL, O_CLOEXEC | O_NONBLOCK);
+                    childPid = -1;
+                }
+            }
             else if (pollfd.revents & POLLERR)
             {
                 kill(childPid, SIGTERM);
@@ -104,7 +113,7 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
         else if (nRead == 0)
         {
             int stat_loc = 0;
-            if (waitpid(childPid, &stat_loc, 0) == childPid)
+            if (childPid > 0 && waitpid(childPid, &stat_loc, 0) == childPid)
             {
                 if (!WIFEXITED(stat_loc))
                     return "child process exited abnormally";
@@ -113,10 +122,15 @@ const char* ffProcessAppendOutput(FFstrbuf* buffer, char* const argv[], bool use
                 // We only handle 127 as an error. See `getTerminalVersionUrxvt` in `terminalshell.c`
                 return NULL;
             }
-            return "waitpid() failed";
+            return NULL;
         }
         else if (nRead < 0)
-            break;
+        {
+            if (errno == EAGAIN)
+                return NULL;
+            else
+                break;
+        }
     };
 
     return "read(childPipeFd, str, FF_PIPE_BUFSIZ) failed";