RFR: 8293887: AArch64 build failure with GCC 12 due to maybe-uninitialized warning in libfdlibm k_rem_pio2.c [v2]

[Hao Sun]

> This warning seems to be a false positive, because 1) array "fq" with elements from index 0 to "jz" has already been initialized as "fw" at line 290 [1], and 2) variable "jz" should be non-negative from the comment at line 99 [2].
> 
> Note-1: GCC warning option -Wmaybe-uninitialized is not a new one. Note-2: x86-64 build with GCC 12 on Ubuntu 22.04 passed in my local test.
> 
> This warning is raised only on GCC 12 + AArch64. I suspect it might be some GCC 12 bug, so I reported it to GCC community [3].
> 
> Since it involves third party code, I think it's better to suppress the warning by simply disabling this warning option in the makefile.
> 
> Testing: Release builds with GCC 9, GCC 11 and GCC 12 passed on Ubuntu 22.04/AArch64 system.
> 
> [1] https://github.com/openjdk/jdk/blob/master/src/java.base/share/native/libfdlibm/k_rem_pio2.c#L290 
> [2] https://github.com/openjdk/jdk/blob/master/src/java.base/share/native/libfdlibm/k_rem_pio2.c#L99 
> [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106992

Hao Sun has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:

 - Disable the warning option per file
   
   After JDK-8294281, we can disable the warning options per file.
   
   Testing: Release builds with GCC 9, GCC 11 and GCC 12 passed on Ubuntu
   22.04/AArch64 system.
 - Merge branch 'master' into 8293887-gcc12-fdlibm
 - 8293887: AArch64 build failure with GCC 12 due to maybe-uninitialized warning in libfdlibm k_rem_pio2.c
   
   This warning seems to be a false positive, because 1) array "fq" with
   elements from index 0 to "jz" has already been initialized as "fw" at
   line 290 [1], and 2) variable "jz" should be non-negative from the
   comment at line 99 [2].
   
   Note-1: GCC warning option -Wmaybe-uninitialized is not a new one.
   Note-2: x86-64 build with GCC 12 on Ubuntu 22.04 passed in my local
   test.
   
   This warning is raised only on GCC 12 + AArch64. I suspect it might be
   some GCC 12 bug, so I reported it to GCC community [3].
   
   Since it involves third party code, I think it's better to suppress the
   warning by simply disabling this warning option in the makefile.
   
   Testing: Release builds with GCC 9, GCC 11 and GCC 12 passed on Ubuntu
   22.04/AArch64 system.
   
   [1] https://github.com/openjdk/jdk/blob/master/src/java.base/share/native/libfdlibm/k_rem_pio2.c#L290
   [2] https://github.com/openjdk/jdk/blob/master/src/java.base/share/native/libfdlibm/k_rem_pio2.c#L99
   [3] https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106992

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/10386/files
  - new: https://git.openjdk.org/jdk/pull/10386/files/f745d060..22355e68

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=10386&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=10386&range=00-01

  Stats: 5636 lines in 151 files changed: 3213 ins; 1665 del; 758 mod
  Patch: https://git.openjdk.org/jdk/pull/10386.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/10386/head:pull/10386

PR: https://git.openjdk.org/jdk/pull/10386