[PATCH] D122976: Bump minimum toolchain version

[James Y Knight via Phabricator via llvm-commits]

jyknight added inline comments.


================
Comment at: llvm/cmake/modules/CheckCompilerVersion.cmake:22
 set(GCC_MIN_DATE 20150422)
-set(GCC_SOFT_ERROR_DATE 20150422)
+set(GCC_SOFT_ERROR_DATE 20170502)
 
----------------
Replace this with `set(LIBSTDCXX_SOFT_ERROR 7)` and use per comment below.


================
Comment at: llvm/cmake/modules/CheckCompilerVersion.cmake:100-101
     endif()
     # Test for libstdc++ version of at least 5.1 by checking for std::iostream_category().
     # Note: We should check _GLIBCXX_RELEASE when possible (i.e., for GCC 7.1 and up).
     check_cxx_source_compiles("
----------------
As this change increments the minimum GCC version to 7, we should switch to using `_GLIBCXX_RELEASE` to check the libstdc++ version. This is better than using `__GLIBCXX__` dates, because the dates are updated for every patch release on every branch, so it cannot actually distinguish between branches properly.

The hack of checking iostream_category can go away, as well (it was just a workaround for the unreliability of GLIBCXX).

So, the whole check below should be able to be simplified to:
```
#if defined(__GLIBCXX__)
#if !defined(_GLIBCXX_RELEASE) || _GLIBCXX_RELEASE < ${LIBSTDCXX_SOFT_ERROR}
#error Unsupported libstdc++ version
#endif
#endif
int main() { return 0; }
```



Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D122976/new/

https://reviews.llvm.org/D122976