output redirection

diff --git a/common.cc b/common.cc
index d9915993c8535c0b9b99ee3ffe0f27ab9aa9ec80..bbb30539a8bd36710d9837614c2823b4f1ed3894 100644 (file)
--- a/common.cc
+++ b/common.cc
@@ -1,15 +1,22 @@
 #include <execinfo.h>
 #include <stdio.h>
 #include <stdlib.h>
+#include <unistd.h>
+#include <errno.h>
+#include <fcntl.h>
 
 #include <model-assert.h>
 
 #include "common.h"
 #include "model.h"
 #include "stacktrace.h"
+#include "output.h"
 
 #define MAX_TRACE_LEN 100
 
+FILE *model_out;
+int fd_user_out; /**< @brief File descriptor from which to read user program output */
+
 #define CONFIG_STACKTRACE
 /** Print a backtrace of the current program state. */
 void print_trace(void)
@@ -52,3 +59,103 @@ void model_assert(bool expr, const char *file, int line)
                model->assert_user_bug(msg);
        }
 }
+
+/**
+ * @brief Setup output redirecting
+ *
+ * Redirects user program's stdout to a pipe so that we can dump it
+ * selectively, when displaying bugs, etc.
+ * Also connects a special file 'model_out' directly to stdout, for printing
+ * data when needed.
+ *
+ * The model-checker can selectively choose to print/hide the user program
+ * output.
+ * @see clear_program_output
+ * @see print_program_output
+ *
+ * Note that the user program's pipe has limited memory, so if a program will
+ * output much data, we will need to buffer it in user-space during execution.
+ * This also means that if ModelChecker decides not to print an execution, it
+ * should promptly clear the pipe.
+ */
+void redirect_output()
+{
+       int fd;
+
+       /* Save stdout for later use */
+       fd = dup(fileno(stdout));
+       model_out = fdopen(fd, "w");
+
+       /* Redirect program output to a pipe */
+       int pipefd[2];
+       if (pipe(pipefd) < 0) {
+               perror("pipe");
+               exit(EXIT_FAILURE);
+       }
+       fd = dup2(pipefd[1], fileno(stdout)); // STDOUT_FILENO
+       close(pipefd[1]);
+
+       /* Save the "read" side of the pipe for use later */
+       fcntl(pipefd[0], F_SETFL, O_NONBLOCK);
+       fd_user_out = pipefd[0];
+}
+
+/**
+ * @brief Wrapper for reading data to buffer
+ *
+ * Besides a simple read, this handles the subtleties of EOF and nonblocking
+ * input (if fd is O_NONBLOCK).
+ *
+ * @param fd The file descriptor to read.
+ * @param buf Buffer to read to.
+ * @param maxlen Maximum data to read to buffer
+ * @return The length of data read. If zero, then we hit EOF or ran out of data
+ * (non-blocking)
+ */
+static ssize_t read_to_buf(int fd, char *buf, size_t maxlen)
+{
+       ssize_t ret = read(fd, buf, maxlen);
+       if (ret < 0) {
+               if (errno == EAGAIN || errno == EWOULDBLOCK) {
+                       return 0;
+               } else {
+                       perror("read");
+                       exit(EXIT_FAILURE);
+               }
+       }
+       return ret;
+}
+
+/** @brief Dump any pending program output without printing */
+void clear_program_output()
+{
+       fflush(stdout);
+       char buf[200];
+       while (read_to_buf(fd_user_out, buf, sizeof(buf)));
+}
+
+/** @brief Print out any pending program output */
+void print_program_output()
+{
+       char buf[200];
+
+       /* Gather all program output */
+       fflush(stdout);
+
+       /* Read program output pipe and write to (real) stdout */
+       int ret;
+       while (1) {
+               ret = read_to_buf(fd_user_out, buf, sizeof(buf));
+               if (!ret)
+                       break;
+               while (ret > 0) {
+                       int res = fwrite(buf, 1, ret, model_out);
+                       if (res < 0) {
+                               errno = ferror(model_out);
+                               perror("fwrite");
+                               exit(EXIT_FAILURE);
+                       }
+                       ret -= res;
+               }
+       }
+}

diff --git a/common.h b/common.h
index b1d6b31ecfe89e4136cee5a368e27534283c0bd6..9c1e1ed384e199fd5e8761d8a37a34ab6787ad61 100644 (file)
--- a/common.h
+++ b/common.h
@@ -8,7 +8,9 @@
 #include <stdio.h>
 #include "config.h"
 
-#define model_print(fmt, ...) do { printf(fmt, ##__VA_ARGS__); } while (0)
+extern FILE *model_out;
+
+#define model_print(fmt, ...) do { fprintf(model_out, fmt, ##__VA_ARGS__); } while (0)
 
 #ifdef CONFIG_DEBUG
 #define DEBUG(fmt, ...) do { model_print("*** %25s(): line %-4d *** " fmt, __func__, __LINE__, ##__VA_ARGS__); } while (0)

diff --git a/main.cc b/main.cc
index f55b98df2a4cbaa66262497fdad58992c8bac5b0..f79366fb2d8450bcbbe69373ac45db600aec8caa 100644 (file)
--- a/main.cc
+++ b/main.cc
@@ -7,6 +7,7 @@
 #include <threads.h>
 #include "common.h"
 #include "threads-model.h"
+#include "output.h"
 
 #include "datarace.h"
 
@@ -145,6 +146,9 @@ int main(int argc, char ** argv) {
        main_argc = argc;
        main_argv = argv;
 
+       /* Configure output redirection for the model-checker */
+       redirect_output();
+
        /* Let's jump in quickly and start running stuff */
        initSnapshotLibrary(10000, 1024, 1024, 4000, &model_main);
 }

diff --git a/model.cc b/model.cc
index bf54ecc10aadf02a1807dec87dd7c013f998a81d..9ed6d423452a52e5c4ee006fa624fad809bdebc3 100644 (file)
--- a/model.cc
+++ b/model.cc
@@ -13,6 +13,7 @@
 #include "promise.h"
 #include "datarace.h"
 #include "threads-model.h"
+#include "output.h"
 
 #define INITIAL_THREAD_ID      0
 
@@ -139,6 +140,10 @@ void ModelChecker::reset_to_initial_state()
        too_many_reads = false;
        bad_synchronization = false;
        reset_asserted();
+
+       /* Print all model-checker output before rollback */
+       fflush(model_out);
+
        snapshotObject->backTrackBeforeStep(0);
 }
 

diff --git a/output.h b/output.h
new file mode 100644 (file)
index 0000000..ca55b7a
--- /dev/null
+++ b/output.h
@@ -0,0 +1,12 @@
+/** @file output.h
+ *  @brief Functions for redirecting program output
+ */
+
+#ifndef __OUTPUT_H__
+#define __OUTPUT_H__
+
+void redirect_output();
+void clear_program_output();
+void print_program_output();
+
+#endif /* __OUTPUT_H__ */