[Bug c++/65301] New: gcc can't detect some uninit reads in ctor init lists

[Bug c++/65301] New: gcc can't detect some uninit reads in ctor init lists

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65301

            Bug ID: 65301
           Summary: gcc can't detect some uninit reads in ctor init lists
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: dcb314 at hotmail dot com

Given the following source code

class K
{
public:
    K * copy();
};

class FunctionExpr
{
public:
    FunctionExpr( const FunctionExpr & );

private:
    K * args;
};

FunctionExpr::FunctionExpr(const FunctionExpr& expr)
        : args(expr.args ? args->copy() : 0)
{
}

then trunk gcc can't detect the read of uninit memory for args->copy.

$ ~/gcc/results/bin/gcc -c -g -O2 -Wall -Wextra -pedantic bug189.cc
$

Here is clang doing the right thing:

$ ~/llvm/results/bin/clang++ -c -g -O2 -Wall -Wextra -pedantic bug189.cc
bug189.cc:18:28: warning: field 'args' is uninitialized when used here
      [-Wuninitialized]
        : args(expr.args ? args->copy() : 0)
                           ^
1 warning generated.
$

[Bug c++/65301] gcc can't detect some uninit reads in ctor init lists

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65301

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Yes, this is well known and a dup of another bug, maybe several.

[Bug c++/65301] gcc can't detect some uninit reads in ctor init lists

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65301

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I pointed out other similar cases in
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=18016#c9 when fixing the simple
case of args(args)

[Bug c++/65301] gcc can't detect some uninit reads in ctor init lists

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65301

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |manu at gcc dot gnu.org
         Resolution|---                         |DUPLICATE

--- Comment #3 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
I think this is relatively easy to fix
(seehttps://gcc.gnu.org/bugzilla/show_bug.cgi?id=19808#c24). I think Anthony
mentioned to me that he got it mostly working, but I haven't heard from him in
a while.

*** This bug has been marked as a duplicate of bug 19808 ***
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Subject: [Bug c++/19808] miss a warning about uninitialized member usage in member initializer list in constructor
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19808

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |dcb314 at hotmail dot com

--- Comment #26 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
*** Bug 65301 has been marked as a duplicate of this bug. ***
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From: "hubicka at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug ipa/65298] [5 Regression] lto1: ICE: in operator[], at vec.h:736 during LTO/PGO Firefox build
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https://gcc.gnu.org/bugzilla/show_bug.cgi?ide298

--- Comment #1 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
lto1: internal compiler error: in operator[], at vec.h:736
0xffc277 vec<tree_node*, va_heap, vl_embed>::operator[](unsigned int)
        ../../gcc/gcc/vec.h:736
0xffd678 vec<tree_node*, va_heap, vl_embed>::operator[](unsigned int)
        ../../gcc/gcc/vec.h:1184
0xffd678 vec<tree_node*, va_heap, vl_ptr>::operator[](unsigned int)
        ../../gcc/gcc/vec.h:1202
0xffd678 ipa_value_from_jfunc(ipa_node_params*, ipa_jump_func*)
        ../../gcc/gcc/ipa-cp.c:937

The out of range access here is caused by pass through function specifying an
index of function parameter that is past the end of ipa-cp lattice.
I suppose it is either some kind of datastructure corruption or a fact that we
manage to inline function call with mismatching arguments?

I saw ICE on this spot in the past and they usually were the first - we forgot
to update correctly after inlining...

What is your -march=native?