Integrated: 8283059: Uninitialized warning in check_code.c with GCC 11.2

[Mikael Vidstedt]

On Thu, 17 Mar 2022 20:56:34 GMT, Mikael Vidstedt <mikael at openjdk.org> wrote:

> Note: this PR replaces the one I messed up earlier.
> 
> 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, 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}

This pull request has now been integrated.

Changeset: d8893fad
Author:    Mikael Vidstedt <mikael at openjdk.org>
URL:       https://git.openjdk.java.net/jdk/commit/d8893fad23d1ee6841336b96c34599643edb81ce
Stats:     30 lines in 1 file changed: 9 ins; 0 del; 21 mod

8283059: Uninitialized warning in check_code.c with GCC 11.2

Reviewed-by: dholmes

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PR: https://git.openjdk.java.net/jdk/pull/7859