Bypass warning reported by gcc

gcc reports a warning:
m_stacktrace.c:183: warning: ‘xip_verified’ may be used uninitialized in this function

This warning is a false positive:
xip_verified is assigned in the following branch:
      if (UNLIKELY(xip_verif >= CFUNWIND)) {
         if (xip_verif == CFUNWIND) {
            ...
         } else {
           <<<< here xip_verified is initialised >>>>
         }
      }

xip_verified is then used only if xip_verif > CFUNWIND.

Assign a rubish value to xip_verified to silence gcc.

(??? there are GCC pragmas that can be used to
disable a warning only on a specific line e.g.
something like:

   #pragma GCC diagnostic ignored "-Wuninitialized"
   Addr xip_verified; // xip for which we have calculated fpverif_uregs
   #pragma GCC diagnostic warning "-Wuninitialized"

instead of
   Addr xip_verified = 0; // xip for which we have calculated fpverif_uregs
   // 0 assigned to silence false positive -Wuninitialized warning

but the #pragma technique seems not used currently.

So, using the bypass by assigning a rubbish value

git-svn-id: svn://svn.valgrind.org/valgrind/trunk@13282

diff --git a/coregrind/m_stacktrace.c b/coregrind/m_stacktrace.c
index e7db9c58775eefcf825ea5e114ef118ba991a83b..26a72724a492afb86f174f87ce25e1bf49ed4892 100644 (file)
--- a/coregrind/m_stacktrace.c
+++ b/coregrind/m_stacktrace.c
@@ -180,7 +180,10 @@ UInt VG_(get_StackTrace_wrk) ( ThreadId tid_if_known,
    vg_assert(sizeof(Addr) == sizeof(void*));
 
    D3UnwindRegs fpverif_uregs; // result of CF unwind for a check reason.
-   Addr xip_verified; // xip for which we have calculated fpverif_uregs
+   Addr xip_verified = 0; // xip for which we have calculated fpverif_uregs
+   // 0 assigned to silence false positive -Wuninitialized warning
+   // This is a false positive as xip_verified is assigned when xip_verif > CFUNWIND
+   // and only used if xip_verif > CFUNWIND.
 
    D3UnwindRegs uregs;
    uregs.xip = (Addr)startRegs->r_pc;