On Wed, Jun 04, 2025 at 02:03:56PM +0200, David Marchand wrote: > On Tue, Jun 3, 2025 at 3:01 AM Andre Muezerie > <andre...@linux.microsoft.com> wrote: > > > > On Wed, Apr 16, 2025 at 02:44:54PM -0700, Andre Muezerie wrote: > > > DPDK uses GCC attribute "used" through macro __rte_used to indicate > > > that a variable not referenced in the code should be assumed being > > > used and therefore not be optimized away. This technique is used to embed > > > information in the binaries, by having crafted information stored in > > > them. > > > > > > MSVC offers similar functionality, but it differs significantly: MSVC > > > requires a pragma to be used to send a command to the linker telling it > > > explicitly the name of the symbol that should be included (even if not > > > referenced). As a side-effect, variables called out to be included cannot > > > be static, otherwise their symbols are not "seen" by the linker. This > > > restriction requires some DPDK code to be refactored. > > > > > > Macro RTE_INCLUDE is used in this patch to ensure these special variables > > > make it to the final binaries. > > > > > > The elimination of "static" for some of these variables caused name > > > clashes when __COUNTER__ predefined macro was used. As a workaround, > > > predefined macro __LINE__ was used instead. However, when __COUNTER__ > > > was used directly from a header file, __LINE__ had to be used from the > > > .c files, otherwise it would also not result in a unique symbol. This > > > required a parameter to be added to some macros so that the __LINE__ > > > could be passed from the .c file to the macro defined in the header > > > (which was originally using __COUNTER__). > > > > > > With this patchset commands like the one below provide the same JSON > > > output as would be obtained on Linux. > > > > > > python usertools\dpdk-pmdinfo.py build\app\dpdk-testpmd.exe > > > > > > v4: > > > - limited the use of __LINE__ to the header files, reducing number of > > > changes made in previous versions of this patchset. > > Open question, since the submission of this series, __rte_used is used > in the new symbol export macros. > It seems those macros are not affected by the problem you described > (and fixed with RTE_INCLUDE). > Is it because the symbols are explicitly listed as exported? >
Correct. When using MSVC, "__rte_used" is stripped away by the preprocessor and therefore has no effect. All required symbols need to be explicitly listed as exported, otherwise the linker will complain about symbols not found. > > -- > David Marchand
