Improve the unused-value check to look into comma expressions and filter out
voids in sub-expressions.  Patch by Mike M!

Fixes PR4806.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@98335 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Sema/return.c b/test/Sema/return.c
index 5d1c97f..3ab23f4 100644
--- a/test/Sema/return.c
+++ b/test/Sema/return.c
@@ -1,4 +1,4 @@
-// RUN: %clang %s -fsyntax-only -Xclang -verify -fblocks -Wno-unreachable-code
+// RUN: %clang %s -fsyntax-only -Xclang -verify -fblocks -Wno-unreachable-code -Wno-unused-value
 
 // clang emits the following warning by default.
 // With GCC, -pedantic, -Wreturn-type or -Wall are required to produce the 
diff --git a/test/Sema/warn-unused-value.c b/test/Sema/warn-unused-value.c
new file mode 100644
index 0000000..2e0fa54
--- /dev/null
+++ b/test/Sema/warn-unused-value.c
@@ -0,0 +1,53 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wunused-value %s
+
+int i = 0;
+int j = 0;
+
+void foo();
+
+// PR4806
+void pr4806() {
+  1,foo();          // expected-warning {{expression result unused}}
+
+  // other
+  foo();
+  i;                // expected-warning {{expression result unused}}
+
+  i,foo();          // expected-warning {{expression result unused}}
+  foo(),i;          // expected-warning {{expression result unused}}
+
+  i,j,foo();        // expected-warning {{expression result unused}}
+  i,foo(),j;        // expected-warning {{expression result unused}}
+  foo(),i,j;        // expected-warning {{expression result unused}}
+
+  i++;
+
+  i++,foo();
+  foo(),i++;
+
+  i++,j,foo();      // expected-warning {{expression result unused}}
+  i++,foo(),j;      // expected-warning {{expression result unused}}
+  foo(),i++,j;      // expected-warning {{expression result unused}}
+
+  i,j++,foo();      // expected-warning {{expression result unused}}
+  i,foo(),j++;      // expected-warning {{expression result unused}}
+  foo(),i,j++;      // expected-warning {{expression result unused}}
+
+  i++,j++,foo();
+  i++,foo(),j++;
+  foo(),i++,j++;
+
+  {};
+  ({});
+  ({}),foo();
+  foo(),({});
+
+  (int)1U;          // expected-warning {{expression result unused}}
+  (void)1U;
+
+  // pointer to volatile has side effect (thus no warning)
+  int* pi = &i;
+  volatile int* pj = &j;
+  *pi;              // expected-warning {{expression result unused}}
+  *pj;
+}
diff --git a/test/SemaCXX/decl-expr-ambiguity.cpp b/test/SemaCXX/decl-expr-ambiguity.cpp
index 81f6839..4243c1c 100644
--- a/test/SemaCXX/decl-expr-ambiguity.cpp
+++ b/test/SemaCXX/decl-expr-ambiguity.cpp
@@ -10,7 +10,7 @@
   int(a)++; // expected-error {{expression is not assignable}}
   __extension__ int(a)++; // expected-error {{expression is not assignable}}
   __typeof(int)(a,5)<<a; // expected-error {{function-style cast to a builtin type can only take one argument}}
-  void(a), ++a; // expected-warning {{expression result unused}}
+  void(a), ++a;
   if (int(a)+1) {}
   for (int(a)+1;;) {} // expected-warning {{expression result unused}}
   a = sizeof(int()+1);
diff --git a/test/SemaCXX/warn-unused-value.cpp b/test/SemaCXX/warn-unused-value.cpp
new file mode 100644
index 0000000..775c3cf
--- /dev/null
+++ b/test/SemaCXX/warn-unused-value.cpp
@@ -0,0 +1,17 @@
+// RUN: %clang_cc1 -fsyntax-only -verify -Wunused-value %s
+
+// PR4806
+namespace test0 {
+  class Box {
+  public:
+    int i;
+    volatile int j;
+  };
+
+  void doit() {
+    // pointer to volatile has side effect (thus no warning)
+    Box* box = new Box;
+    box->i; // expected-warning {{expression result unused}}
+    box->j;
+  }
+}