Fix some Pervasive Clang Warnings #250
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The `bmqa::MessageImpl` class is declared in the `bmqa_message` component as a `struct`, but is forward-declared in `bmqt_subscription` as a `class`. This is valid C++ with our desired semantics, but the clang still warns that under the Microsoft C++ ABI, this may result in linker errors. Although we do not support Windows as a target platform, this warning is pernitious: many components that use `bmqt_subscription` will see this warning; including those of users! While it would be easy to turn off this warning, this patch instead fixes the warning by changing the `class` forward declaration in `bmqt_subscription` to match the `struct` declaration in `bmqa_message`. Signed-off-by: Patrick M. Niedzielski <[email protected]>
The supported compiler on modern MacOS systems is clang; the `gcc` command forwards to `clang` underlyingly, unless a user explicitly installs GCC. Unfortunately, our build system was assuming GCC as the compiler on MacOS systems. For the most part, this had no adverse effects, as the two frontends attempt to be compatible. However, there is one warning that GCC supports that clang does not, which we were inadvertently passing: `-Wlogical-op`, which in clang is superseded by `-Wlogical-op-parentheses`. The primary issue here is that the we outsource some of our CMake configuration to BDE Tools, but we need to manually select which platform to use. This patch manually selects `clang` rather than `gcc` in the `bin/build-darwin.sh` script, which silences the above warning. Signed-off-by: Patrick M. Niedzielski <[email protected]>
The BDE idiom for using `BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES`
is by using it in the condition of a preprocessor conditional `#if`, as
follows:
#if !BSLS_COMPILERFEATURES_SIMULATE_CPP11_FEATURES
When compiling on a platform that supports C++11, this macro is
undefined; the behavior in this situation is well-defined, though, and
the macro is replaced with `0`, rendering the above condition true.
Clang, however, warns in this situation, letting us know that we are
expanding a macro that is undefined to `0`, which we may not want to do.
Because of how commonly we use this idiom in our codebase, this patch
turns off this warning across all files.
Signed-off-by: Patrick M. Niedzielski <[email protected]>
pniedzielski
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hallfox
approved these changes
Apr 16, 2024
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When compiling the BlazingMQ on a modern version of Clang on a Mac, we get many more warnings that we do not see on GCC. Often, these warnings are on code in header files, and so they are repeated for every translation unit that includes these headers. This PR fixes three such warnings, cutting down on the number of warnings for each compilation significantly: fixing
-Wmismatched-tags, using the proper BDE configuration for Clang, and disabling a warning for intended preprocessor behavior. Please see commit messages for each patch for more details.