[gdal-dev] clang-tidy 23 bugprone-signed-bitwise and CPL_LSBINT32PTR macros

[Even Rouault]

Please re-try with the latest pushed commit in the PR that should 
hopefully make -Wsign-conversion happy

Le 11/05/2026 à 14:11, Andrew C Aitchison via gdal-dev a écrit :
> On Sun, 10 May 2026, Even Rouault wrote:
>
>> Andrew,
>>
>> does https://github.com/OSGeo/gdal/pull/14524 fix the warning?
>
> With that change, clang-tidy is happy, but now the compile breaks if I 
> use
> `clang++ -Wsign-conversion`:
>
> In file included from /usr/local/gdal/git.llvm/include/gdal_dataset.h:18:
> /usr/local/gdal/git.llvm/include/cpl_port.h:808:33: error: implicit 
> conversion changes signedness: 'int' to 'uint32_t' (aka 'unsigned int')
>       [-Werror,-Wsign-conversion]
>   808 |         uint32_t unsigned_val = CPL_LSBINT32PTR(x);
>       |                  ~~~~~~~~~~~~   ^~~~~~~~~~~~~~~~~~
> /usr/local/gdal/git.llvm/include/cpl_port.h:788:62: note: expanded 
> from macro
>       'CPL_LSBINT32PTR'
>   786 |     ((*CPL_REINTERPRET_CAST(const GByte *, x)) 
> |                     \
>       | 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   787 |      (*((CPL_REINTERPRET_CAST(const GByte *, x)) + 1) << 8) 
> |        \
>       | 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   788 |      (*((CPL_REINTERPRET_CAST(const GByte *, x)) + 2) << 16) 
> |       \
>       | 
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
>   789 |      (*((CPL_REINTERPRET_CAST(const GByte *, x)) + 3) << 24))
>       | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> qed.cpp:122:30: note: in instantiation of function template 
> specialization
>       'CPL_LSBSINT32PTR<unsigned char>' requested here
>   122 |     return (static_cast<int>(CPL_LSBSINT32PTR(buf)));
>       |                              ^
>
>
>
>> Even
>>
>> Le 10/05/2026 à 16:02, Andrew C Aitchison via gdal-dev a écrit :
>>>
>>> clang-tidy 23 (I'm using Ubuntu 26.04 with build
>>> ++20260508083129+d791e3a6f4c8-1~exp1~20260508083148.481
>>> from llvm-toolchain-snapshot at https://www.llvm.org/)
>>> has a new? check bugprone-signed-bitwise.
>>>
>>> This check objects to macros like CPL_LSBINT32PTR:
>>>
>>> clang-tidy --config="{Checks: 'bugprone-signed-bitwise', 
>>> CheckOptions: 
>>> {bugprone-signed-bitwise.IgnorePositiveIntegerLiterals: true}}" 
>>> frmts/raw/lcpdataset.cpp
>>>
>>> reports 63 warnings of [bugprone-signed-bitwise], starting with:
>>>
>>> /home/werdna/gdal/git/frmts/raw/lcpdataset.cpp:171:10: warning: use 
>>> of a signed integer operand with a binary bitwise operator 
>>> [bugprone-signed-bitwise]
>>>   171 |     if ((CPL_LSBSINT32PTR(poOpenInfo->pabyHeader) != 20 &&
>>>       |          ^
>>> /usr/local/gdal/git.llvm/include/cpl_port.h:799:53: note: expanded 
>>> from macro 'CPL_LSBSINT32PTR'
>>>   799 | #define CPL_LSBSINT32PTR(x) CPL_STATIC_CAST(GInt32, 
>>> CPL_LSBINT32PTR(x))
>>>       | ~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~
>>> /usr/local/gdal/git.llvm/include/cpl_port.h:786:6: note: expanded 
>>> from macro 'CPL_LSBINT32PTR'
>>>   786 |     ((*CPL_REINTERPRET_CAST(const GByte *, x)) 
>>> |                  \
>>>       |      ^
>>>   787 |      (*((CPL_REINTERPRET_CAST(const GByte *, x)) + 1) << 8U) 
>>> |    \
>>>   788 |      (*((CPL_REINTERPRET_CAST(const GByte *, x)) + 2) << 
>>> 16U) |   \
>>> |                                                               ~
>>> /usr/local/gdal/git.llvm/include/cpl_port.h:181:55: note: expanded 
>>> from macro 'CPL_STATIC_CAST'
>>>   181 | #define CPL_STATIC_CAST(type, expr) static_cast<type>(expr)
>>>       | ^~~~
>>>
>>> I suspect that default type-promotion from an unsigned GByte
>>> to a *signed* int does not help here.
>>>
>>> Not exactly a bug, but annoying.
>>>
>
>
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