[C++-sig] boost/python 1.33.1 breaks aliasing rules (original) (raw)
Philipp Thomas pth at suse.de
Thu Dec 1 17:19:31 CET 2005
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We use a patch for gcc 4.1 that also makes it warn about violations of the C/C++ aliasing rules in C++ code (stock gcc only warns for C code). For the code in boost 1.33.1 I get
warning: dereferencing type-punned pointer will break strict-aliasing rules
for the following files:
/usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/long.cpp: 12,19, 26 /usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/dict.cpp: 32 /usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/tuple.cpp:12 /usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/str.cpp: 12 /usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/object/class.cpp:543,553 /usr/src/packages/BUILD/boost_1_33_1/libs/python/build/../src/list.cpp: 15
As our package build system treats this type of warning as errors, I will use -fno-strict-aliasing for gcc as I'm not familiar with that code and I want to get the package built.
For boost you should also consider either using said gcc switch or fix the code to not break strict-aliasing rules as such code leads gcc to opmize in a way it shouldn't (for instance by eliminating variables which makes access through a type-punned pointer return garbage).
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