c++: allow removing inline comments from devicetree_generated.h
#86758
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This test case is meant to test the use of preprocessor macros that
paste together a number from devicetree with a suffix, like UINT32_C.
The test case is expected to fail because the C++ preprocessor does not
elide comments added by gen_dts_defines.py before expanding the macros,
resulting in errors like the following:
error: pasting "/* 0x2 */" and "U" does not give
a valid preprocessing token
or, in this synthetic test case:
error: unable to find numeric literal operator 'operator""UU'
when accessing values from the devicetree_generated.h header file.
Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
pillo79
changed the title
devicetree_generated.h
Add an option to remove inline comments from the #define lines. This allows including the generated files in C++ code, which does not elide the comments when performing macro expansion. Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
The DTS extraction process generates headers with inline comments, which are not ignored properly by the C++ preprocessor. This is causing build failures when using devicetree macros in C++ code. Add a note to the C++ documentation to inform users about the issue and how to work around it, and update the C++ test case. Signed-off-by: Luca Burelli <l.burelli@arduino.cc>
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Closing after additional investigation as I have identified the actual cause - a nested macro expansion fixed by arduino/ArduinoCore-zephyr@1eade10 . Nothing related to C++. 🤦♂️ |
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Preprocessor macros that paste together a number with a suffix, like
UINT32_C, do not currently work properly in C++ code for some types of device tree data, such as theregproperty. This is becausegen_defines.pyadds inline comments to those entries in thedevicetree_generated.hfiles, and this confuses the C++ preprocessor during macro expansion, resulting in errors like the following:or, in the synthetic test case added in this PR:
This may be verified by running
twister -T tests/lib/cpp/cxxon just the first commit of this PR, as done in this CI run. Also, an actual example in a downstream project: arduino/ArduinoCore-zephyr#80 (comment) .This PR fixes the issue by adding an option to the
gen_defines.py, using it in the C++ test and mentioning it in the C++ documentation page for downstream users.