Created attachment 1501630 [details]
test program snippet that triggers the report

Description of problem:

Valgrind is reporting what I suspect is a false positive:

"Conditional jump or move depends on uninitialised value" on
glibc strcmp-avx2.S:113

I've created a test program attached that generates the report using wcsncmp.  It appears to be length dependant on the underlying memory that is allocated.
This did not appear in versions of Fedora prior to 29.

The output of the test program is below.

[root@localhost net]# gcc test.c
[root@localhost net]# valgrind ./a.out
==26675== Memcheck, a memory error detector
==26675== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26675== Using Valgrind-3.14.0 and LibVEX; rerun with -h for copyright info
==26675== Command: ./a.out
==26675== 


first test case (8 wchar_t), no complaints from valgrind
test case 1 match


second test case (6 wchar_t), valgrind complains
==26675== Conditional jump or move depends on uninitialised value(s)
==26675==    at 0x49C4E59: __wcsncmp_avx2 (strcmp-avx2.S:113)
==26675==    by 0x40121B: main (in /home/russell/net/a.out)
==26675== 
test case 2 match
==26675== 
==26675== HEAP SUMMARY:
==26675==     in use at exit: 0 bytes in 0 blocks
==26675==   total heap usage: 3 allocs, 3 frees, 1,080 bytes allocated
==26675== 
==26675== All heap blocks were freed -- no leaks are possible
==26675== 
==26675== For counts of detected and suppressed errors, rerun with: -v
==26675== Use --track-origins=yes to see where uninitialised values come from
==26675== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)


Version-Release number of selected component (if applicable):

valgrind-3.14.0-1.fc29.x86_64