[LLVMbugs] [Bug 9824] New: add -Wunused-but-set-variable

bugzilla-daemon at llvm.org bugzilla-daemon at llvm.org
Sun May 1 18:59:50 PDT 2011


           Summary: add -Wunused-but-set-variable
           Product: clang
           Version: unspecified
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: nicholas at mxc.ca
                CC: llvmbugs at cs.uiuc.edu

GCC 4.6 has a nice warning part of -Wall which warns on variables that are used
by being set, but never read or have their address taken. We should add
-Wunused-but-set-variable to clang.

Here's a few examples of how the warning behaves in GCC:

  void test1() {
    int i = 0;  // -Wunused-but-set-variable warning
    i = 1;

  void test2() {
    int i = 0;  // no warning
    i = 1;
    &i;  // -Wunused-value warning

  void test3() {
    int i = 1;  // -Wunused-variable warning, not -Wunused-but-set-variable.

  void use(int);
  void test4() {
    int i = 0;  // no warning

which seems eminently sane to me.

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