[cfe-dev] provide a hint to clang-analyzer-optin.portability.UnixAPI?

[Artem Dergachev via cfe-dev]

Yeah but it doesn't help much, i'm more interested in intermediate 
events across the path.

On 3/16/20 8:50 PM, Balázs Benics wrote:
> I might be wrong, but probably this is the line which triggered the 
> warning.
> https://github.com/robertu94/libpressio/blob/master/include/libpressio_ext/cpp/data.h#L247
>
>
> On Mon, Mar 16, 2020, 05:35 Artem Dergachev via cfe-dev 
> <cfe-dev at lists.llvm.org <mailto:cfe-dev at lists.llvm.org>> wrote:
>
>     It looks like we don't understand that size_in_bytes() always returns
>     the same value. There may be multiple reasons for this. I'd like
>     to see
>     the whole code in order to understand what's going on. Could you
>     produce
>     a preprocessed file and attach it together with the analyzer
>     invocation?
>
>     As a workaround / suppression you should be able to do something
>     like this:
>
>        static void *make_data_ptr(RHS rhs) {
>          if (!rhs.has_data())
>            return nullptr;
>
>          size_t size = rhs.size_in_bytes();
>          return size ? malloc(size) : nullptr;
>        }
>
>        Ctor(RHS rhs): data_ptr(make_data_ptr(rhs)) {}
>
>     This would prevent the analyzer (and, well, your actual generated
>     code)
>     from calling size_in_bytes() twice and believing that it may
>     return two
>     different values.
>
>     On 2/28/20 5:41 PM, Robert Underwood via cfe-dev wrote:
>     >
>     > To whom it may concern,
>     >
>     > tl;dr I think I found a bug in the clang static analyzer. Could
>     > someone please help me find a workaround/where to properly
>     report the bug?
>     >
>     > I have a statement in a class initializer list:
>     >
>     > |data_ptr((rhs.has_data() && rhs.size_in_bytes() > 0)?
>     > malloc(rhs.size_in_bytes()) : nullptr)|
>     >
>     > rhs.has_data() is a const function that returns t/f if
>     rhs.data_ptr !=
>     > null
>     >
>     > rhs.size_in_bytes() a const function that returns the number of
>     bytes
>     > in the structure *if has_data was true*
>     >
>     > i.e. it is possible that rhs.has_data() is false, and
>     > rhs.size_in_bytes() > 0
>     >
>     > However the clang static analyzer seems to get a false positive
>     here.
>     >
>     >
>     |/usr/lib/gcc/x86_64-pc-linux-gnu/8.3.0/include/g++-v8/bits/unique_ptr.h:831:34:
>
>     > note: Calling copy constructor for 'pressio_data'
>     > ../include/libpressio_ext/cpp/data.h:247:15: note: Left side of
>     '&&'
>     > is true data_ptr((rhs.has_data() && rhs.size_in_bytes() > 0)?
>     > malloc(rhs.size_in_bytes()) : nullptr), ^
>     > ../include/libpressio_ext/cpp/data.h:247:33: note: Assuming the
>     > condition is true data_ptr((rhs.has_data() && rhs.size_in_bytes() >
>     > 0)? malloc(rhs.size_in_bytes()) : nullptr), ^
>     > ../include/libpressio_ext/cpp/data.h:247:14: note: '?' condition is
>     > true data_ptr((rhs.has_data() && rhs.size_in_bytes() > 0)?
>     > malloc(rhs.size_in_bytes()) : nullptr), ^
>     > ../include/libpressio_ext/cpp/data.h:247:66: note: Calling
>     > 'pressio_data::size_in_bytes' data_ptr((rhs.has_data() &&
>     > rhs.size_in_bytes() > 0)? malloc(rhs.size_in_bytes()) : nullptr), ^
>     > ../include/libpressio_ext/cpp/data.h:384:12: note: Calling
>     > 'data_size_in_bytes<unsigned long>' return
>     > data_size_in_bytes(data_dtype, num_dimensions(), dims.data()); ^
>     > ../include/libpressio_ext/cpp/data.h:31:5: note: Returning zero
>     return
>     > data_size_in_elements(dimensions, dims) *
>     pressio_dtype_size(type); ^
>     > ../include/libpressio_ext/cpp/data.h:384:12: note: Returning from
>     > 'data_size_in_bytes<unsigned long>' return
>     > data_size_in_bytes(data_dtype, num_dimensions(), dims.data()); ^
>     > ../include/libpressio_ext/cpp/data.h:384:5: note: Returning zero
>     > return data_size_in_bytes(data_dtype, num_dimensions(),
>     dims.data());
>     > ^ ../include/libpressio_ext/cpp/data.h:247:66: note: Returning from
>     > 'pressio_data::size_in_bytes' data_ptr((rhs.has_data() &&
>     > rhs.size_in_bytes() > 0)? malloc(rhs.size_in_bytes()) : nullptr), ^
>     > ../include/libpressio_ext/cpp/data.h:247:59: note: Call to 'malloc'
>     > has an allocation size of 0 bytes data_ptr((rhs.has_data() &&
>     > rhs.size_in_bytes() > 0)? malloc(rhs.size_in_bytes()) : nullptr), |
>     >
>     > Is there a way to instruct the static analyzer that malloc
>     cannot be
>     > called with size_in_bytes == 0 because saying
>     (rhs.size_in_bytes() >
>     > 0) isn’t enough. I’m using clang-9.0.1 on gentoo.
>     >
>     > Respectfully,
>     > Robert Underwood
>     >
>     >
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