RFR: 8283059: Uninitialized warning in check_code.c with GCC 11.2 [v2]

[Mikael Vidstedt]

> Background, from JBS:
> 
> src/java.base/share/native/libverify/check_code.c: In function 'read_all_code': 
> src/java.base/share/native/libverify/check_code.c:942:5: error: 'lengths' may be used uninitialized [-Werror=maybe-uninitialized] 
>   942 | check_and_push(context, lengths, VM_MALLOC_BLK); 
>       | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 
> src/java.base/share/native/libverify/check_code.c:4145:13: note: by argument 2 of type 'const void *' to 'check_and_push' declared here 
>  4145 | static void check_and_push(context_type *context, const void *ptr, int kind) 
>       | ^~~~~~~~~~~~~~ 
> 
> 
> Because the second argument of check_and_push is "const void*" GCC assumes that the malloc:ed data, which has not yet been initialized, will not be/can not be modified later which in turn suggests it may be used without ever being initialized. 
> 
> The same general issue was addressed in [JDK-8266168](https://bugs.openjdk.java.net/browse/JDK-8266168), presumably for GCC 11.1.
> 
> 
> Details:
> 
> Instead of sprinkling more calloc calls around or using pragmas/gcc attributes I chose to change the check_and_push function to take a (non-const) void* argument, and provide a new wrapper function `check_and_push_const` which handles the const argument case. For the (non-const) VM_MALLOC_BKP that means the pointer never needs to go through a const conversion.
> 
> To avoid having multiple ways of solving the same problem I also chose to revert the change made in JDK-8266168, reverting the calloc back to a malloc call.
> 
> Testing:
> 
> tier1 + builds-tier{2,3,4,5}

Mikael Vidstedt has updated the pull request incrementally with 50 additional commits since the last revision:

 - Spell out check_and_push_malloc_block
 - Fix code
 - 8282773: Refactor parsing of integer VM options
   
   Reviewed-by: dholmes, kbarrett
 - 8283274: Improve @jvms usage in java.base
   
   Reviewed-by: iris
 - 8283188: Build time regression caused by JDK-8278917
   
   Reviewed-by: kbarrett, tschatzl
 - 8283320: Error message for Windows libraries always points to --with-msvcr-dll no matter the actual file name
   
   Reviewed-by: erikj, ihse
 - 8283056: show abstract machine code in hs-err for all VM crashes
   
   Reviewed-by: thartmann, dholmes
 - 8282727: Parallel: Remove PSPromotionManager::_totally_drain
   
   Reviewed-by: tschatzl, kbarrett
 - 8281146: Replace StringCoding.hasNegatives with countPositives
   
   Co-authored-by: Lutz Schmidt <lucy at openjdk.org>
   Co-authored-by: Martin Doerr <mdoerr at openjdk.org>
   Reviewed-by: kvn, lucy, rriggs
 - 8282602: Refactor awt classes javadoc to use @throws instead of @exception
   
   Reviewed-by: aivanov, prr
 - ... and 40 more: https://git.openjdk.java.net/jdk/compare/baf72097...eb04d78a

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

Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7794/files
  - new: https://git.openjdk.java.net/jdk/pull/7794/files/baf72097..eb04d78a

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7794&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7794&range=00-01

  Stats: 5146 lines in 353 files changed: 2567 ins; 553 del; 2026 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7794.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7794/head:pull/7794

PR: https://git.openjdk.java.net/jdk/pull/7794