On Mon, 2 Feb 2026 12:45:50 GMT, Leo Korinth <[email protected]> wrote:

> Allow conversion warnings in subsets of the code base. By allowing this, we 
> can improve the code base in parts, and see that those parts do not regress 
> in the future.
> 
> My approach to implement this is by adding support to our make system to 
> recognise and handle "variable packs". A "variable pack" is a list of quoted 
> variable "appendings". It will be picked up by `NamedParamsMacroTemplate` and 
> there recognised by the lack of an assignment operator that is always used 
> when sending variables to macros today. To support sending lists of "variable 
> appendings", the appendings must quote assignment, spaces and quotes. This 
> would be cleanest to implement by hex or base64 encode the string. However, 
> this is extremely hard to do in make, and I prefer not calling the likes of 
> `od` or `base64` to make the code portable and fast.
> 
> With this infrastructure I implement a simple recursive utility to find all 
> files matching a pattern in a folder; I then transform that list to variable 
> assignments that will add compiler warnings for those files.
> 
> This approach is extremely flexible. I can for example combine many calls to 
> the `overrideFlags` macro with different source directories and different 
> patterns.
> 
> The macro will expand to something like (depending on compiler): 
> `module_file1.cpp_CXXFLAGS+=-Wconversion`
> `module_file2.cpp_CXXFLAGS+=-Wconversion`
> 
> this can flexibly be combined with other flags to overlap: 
> `module_file2.cpp_CXXFLAGS+=$(SPACE)-Wotherflag`
> `module_file3.cpp_CXXFLAGS+=$(SPACE)-Wotherflag`
> 
> (note the overlapping sets of flags `file1 -Wconversion`, `file2 -Wconversion 
> -Wotherflag`, `file3 -Wotherflag`)

I will revert the line `$(call 
overrideFlags,$(TOPDIR)/src/hotspot/share/gc/g1,g1ConcurrentMark.cpp,_CXXFLAGS,$(CFLAGS_CONVERSION_WARNINGS)),
 ` if I integrate. The line is there to show the compilation error when adding 
conversion warnings.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/29523#issuecomment-3834925512

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