diff options
| author | Guido Aulisi <guido.aulisi@gmail.com> | 2016-07-22 15:26:29 +0200 |
|---|---|---|
| committer | David Kastrup <dak@gnu.org> | 2016-07-23 14:45:27 +0200 |
| commit | b0dce76daf27721ba157cd2ac5d7662d4c8d75f8 (patch) | |
| tree | 0a55133262bd8c2642454f752092e05e9f786ea7 | |
| parent | b680788cd1c671d52819d69e9e130ff45361a590 (diff) | |
Issue 4814: grob.cc segfaults with gcc6
From the release notes of GCC 6:
Optimizations remove null pointer checks for this
When optimizing, GCC now assumes the this pointer can never be null,
which is guaranteed by the language rules. Invalid programs which
assume it is OK to invoke a member function through a null
pointer (possibly relying on checks like this != NULL) may crash or
otherwise fail at run time if null pointer checks are optimized
away. With the -Wnull-dereference option the compiler tries to warn
when it detects such invalid code.
If the program cannot be fixed to remove the undefined behavior then
the option -fno-delete-null-pointer-checks can be used to disable
this optimization. That option also disables other optimizations
involving pointers, not only those involving this.
As a consequence, we cannot call a member function on a prospective null
pointer (which actually is a bad idea for a number of other reasons,
like when anything tries accessing the vtable) and then try sorting out
the condition in the routine itself.
This problem was first observed with Fedora 24. The Ubuntu GCC6
prerelease does not show this problem; presumably the respective
optimization has been disabled in the Ubuntu/Debian packaging because of
affecting other programs.
Commit-message-by: David Kastrup <dak@gnu.org>
Signed-off-by: David Kastrup <dak@gnu.org>
| -rw-r--r-- | lily/grob.cc | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/lily/grob.cc b/lily/grob.cc index 7ce89d5015..eafa66288e 100644 --- a/lily/grob.cc +++ b/lily/grob.cc @@ -333,7 +333,7 @@ Real Grob::relative_coordinate (Grob const *refp, Axis a) const { /* eaa - hmmm, should we do a programming_error() here? */ - if ((this == NULL) || (refp == this)) + if (refp == this) return 0.0; /* We catch PARENT_L_ == nil case with this, but we crash if we did @@ -342,7 +342,8 @@ Grob::relative_coordinate (Grob const *refp, Axis a) const if (refp == dim_cache_[a].parent_) return off; - off += dim_cache_[a].parent_->relative_coordinate (refp, a); + if (dim_cache_[a].parent_ != NULL) + off += dim_cache_[a].parent_->relative_coordinate (refp, a); return off; } |