New intrinsic: klee_is_replay

This instrinsic detects whether the program is being executed
symbolically or concretely (i.e., using the libkleeRuntest library).

The intended usage (illustrated in the test program) is to
allow the test program to display the input values by invoking
any libraries it wants to.

This is especially valuable if you are constructing complex,
structured values and for languages like Rust (or C++) that have
rich libraries and print libraries.
For example, you might pick a symbolic value N with the
assumption "0 <= N < 10" and then pick N symbolic
values and write them to an array.
The resulting ktest file is a bit hard to understand compared with the
output of the standard print function in Rust/C++.

1 files changed, 33 insertions, 0 deletions

diff --git a/test/Replay/libkleeruntest/replay_detection.c b/test/Replay/libkleeruntest/replay_detection.c
new file mode 100644
index 00000000..7516ecd1
--- /dev/null
+++ b/test/Replay/libkleeruntest/replay_detection.c
@@ -0,0 +1,33 @@
+// RUN: %clang %s -emit-llvm -g %O0opt -c -o %t.bc
+// RUN: rm -rf %t.klee-out
+// RUN: %klee --output-dir=%t.klee-out %t.bc
+//
+// There should be a unique solution
+// RUN: test -f %t.klee-out/test000001.ktest
+// RUN: test ! -f %t.klee-out/test000002.ktest
+
+// Now try to replay with libkleeRuntest
+// RUN: %cc %s %libkleeruntest -Wl,-rpath %libkleeruntestdir -o %t_runner
+// RUN: env KTEST_FILE=%t.klee-out/test000001.ktest %t_runner | FileCheck %s
+
+#include "klee/klee.h"
+#include <stdio.h>
+
+int main(int argc, char** argv) {
+  int x = 0;
+  klee_make_symbolic(&x, sizeof(x), "x");
+
+  if (klee_is_replay()) { // only print x on replay runs
+    printf("x = %d\n", x);
+  }
+
+  // For the sake of testing, these constraints have a single solution
+  klee_assume(40 < x);
+  klee_assume(x < 43);
+  klee_assume((x & 1) == 0);
+
+  return 0;
+}
+
+// When replaying, it should print the concrete value it is running with
+// CHECK: x = 42