Enable hardening flags where available #1501
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Change the commit summary to "Enable compiler sanity" and I'll merge in a whim 😄 Not really joking about that BTW. But actually do explain the different options in the commit message more thoroughly. It's possible (likely even) that other compilers need similar treatment but different flags, and they shouldn't have to chase around for gcc online docs to see what magic it is that these rather obscure flags do. Oh and feel free to add |
We want to remove as many forms of undefined behavior as we can. This adds flags to make integer and pointer overflows well-defined. Furthermore, it turns on strong stack protection. Specifically: - `-fwrapv` tells GCC and Clang that signed integers should have 2’s complement semantics. - `-fwrapv-pointer` tells GCC that pointer arithmetic overflow can wrap, and therefore that out-of-bounds pointer arithmetic is well-defined. - `-fno-strict-overflow` is the same as both of the above flags on GCC, and `-fwrapv` on clang. I included it for completeness. - `-fno-strict-aliasing` turns off the strict-aliasing rule. - `-fstack-protector-all` turns on stack canaries for all functions. - `-fno-delete-null-pointer-checks` makes dereferencing NULL well-defined on GCC. - `-fstack-check` checks for stack overflows. - `-fstack-clash-protection` prevents stack-clash attacks - `-fcf-protection=full` enables control-flow integrity where available - `-D_FORTIFY_SOURCE=2` and `-D_GLIBCXX_ASSERTIONS` enable hardening features in the C and C++ libraries, respectively.
DemiMarie
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I asked you to add one specific flag, not everything in gcc manual. Also like said, I was not joking about the compiler sanity part - hardening flags are a job for distros to choose (that -fstack-protector should rather be removed than more of that kind added), but fundamental compiler behavior is an upstream matter. |
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I'll handle this separately. Thanks for the suggestion though. |
We want to remove as many forms of undefined behavior as we can. This
adds flags to make integer and pointer overflows well-defined.
Furthermore, it turns on strong stack protection.