Kefu Chai 9355a32b5c utils/loading_cache: s/typeof/decltype/ ...

`typeof` is a GNU extension, and is part of C23, but it is not included
by C++23.

if we compile the tree with c++23 instead of gnu++23, the compilation
fails like:

```
FAILED: repair/CMakeFiles/repair.dir/RelWithDebInfo/repair.cc.o
/home/kefu/.local/bin/clang++ -DSCYLLA_BUILD_MODE=release -DXXH_PRIVATE_API -DCMAKE_INTDIR=\"RelWithDebInfo\" -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/gen -isystem /home/kefu/dev/scylladb/abseil -isystem /home/kefu/dev/scylladb/seastar/include -isystem /home/kefu/dev/scylladb/build/RelWithDebInfo/seastar/gen/include -isystem /usr/include/p11-kit-1 -ffunction-sections -fdata-sections -O3 -g -gz -std=gnu++23 -fvisibility=hidden -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-deprecated-copy -Wno-mismatched-tags -Wno-missing-field-initializers -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-unused-parameter -ffile-prefix-map=/home/kefu/dev/scylladb/build=. -march=westmere -Xclang -fexperimental-assignment-tracking=disabled -mllvm -inline-threshold=2500 -fno-slp-vectorize -std=c++23 -Werror=unused-result -DSEASTAR_API_LEVEL=7 -DSEASTAR_SSTRING -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_LOGGER_TYPE_STDOUT -DFMT_SHARED -DWITH_GZFILEOP -MD -MT repair/CMakeFiles/repair.dir/RelWithDebInfo/repair.cc.o -MF repair/CMakeFiles/repair.dir/RelWithDebInfo/repair.cc.o.d -o repair/CMakeFiles/repair.dir/RelWithDebInfo/repair.cc.o -c /home/kefu/dev/scylladb/repair/repair.cc
In file included from /home/kefu/dev/scylladb/repair/repair.cc:21:
In file included from /home/kefu/dev/scylladb/service/storage_service.hh:19:
In file included from /home/kefu/dev/scylladb/service/qos/service_level_controller.hh:19:
In file included from /home/kefu/dev/scylladb/auth/service.hh:23:
In file included from /home/kefu/dev/scylladb/auth/permissions_cache.hh:22:
/home/kefu/dev/scylladb/utils/loading_cache.hh:754:66: error: use of undeclared identifier 'typeof'; did you mean 'typeid'?
  754 |         static_assert(SectionHitThreshold <= std::numeric_limits<typeof(_touch_count)>::max() / 2, "SectionHitThreshold value is too big");
      |                                                                  ^
/home/kefu/dev/scylladb/utils/loading_cache.hh:754:66: error: template argument for template type parameter must be a type
  754 |         static_assert(SectionHitThreshold <= std::numeric_limits<typeof(_touch_count)>::max() / 2, "SectionHitThreshold value is too big");
      |                                                                  ^~~~~~~~~~~~~~~~~~~~
/usr/lib/gcc/x86_64-redhat-linux/14/../../../../include/c++/14/limits:311:21: note: template parameter is declared here
  311 |   template<typename _Tp>
      |                     ^
2 errors generated.
```

in this change, we trade `typeof` for a more standard compliant
`decltype`.

Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>

Closes scylladb/scylladb#21116

2024-10-17 13:41:15 +03:00

35 KiB

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