std lib test suite is not valgrind clean

[andrewrk]

Example of how to reproduce:

$ stage3/bin/zig test ../lib/std/std.zig  -lc -fllvm -femit-bin=test -target x86_64-native
$ valgrind ./test

Just a few examples (there are many more):

==1589188== Use of uninitialised value of size 8
==1589188==    at 0x2956983: memcpy (memcpy.zig:0)
==1589188==    by 0x24BDB5F: multi_array_list.MultiArrayList(zig.Ast.TokenList__struct_289020).setCapacity (multi_array_list.zig:472)
==1589188==    by 0x24B3B3C: multi_array_list.MultiArrayList(zig.Ast.TokenList__struct_289020).ensureTotalCapacity (multi_array_list.zig:424)
==1589188==    by 0x24B3AB0: multi_array_list.MultiArrayList(zig.Ast.TokenList__struct_289020).ensureUnusedCapacity (multi_array_list.zig:447)
==1589188==    by 0x24B3B95: multi_array_list.MultiArrayList(zig.Ast.TokenList__struct_289020).append (multi_array_list.zig:253)
==1589188==    by 0x24B15C9: zig.Ast.parse (Ast.zig:156)
==1589188==    by 0x2684083: Build.Step.Options.decltest.Options (Options.zig:682)
==1589188==    by 0x155656A: test_runner.mainTerminal (test_runner.zig:218)
==1589188==    by 0x1550791: test_runner.main (test_runner.zig:66)
==1589188==    by 0x154FF2D: callMain (start.zig:618)
==1589188==    by 0x154FF2D: callMainWithArgs (start.zig:587)
==1589188==    by 0x154FF2D: main (start.zig:602)

==1589188== Use of uninitialised value of size 8
==1589188==    at 0x24B6BEA: zig.Parse.tokenTag (Parse.zig:15)
==1589188==    by 0x24D7403: zig.Parse.parseTypeExpr (Parse.zig:1923)
==1589188==    by 0x24C0F15: zig.Parse.expectTypeExpr (Parse.zig:1962)
==1589188==    by 0x24DB111: zig.Parse.parseVarDeclProto (Parse.zig:769)
==1589188==    by 0x24DBD64: zig.Parse.parseGlobalVarDecl (Parse.zig:835)
==1589188==    by 0x24DCD49: zig.Parse.expectTopLevelDecl (Parse.zig:648)
==1589188==    by 0x24C1C8C: zig.Parse.expectTopLevelDeclRecoverable (Parse.zig:659)
==1589188==    by 0x24B5864: zig.Parse.parseContainerMembers (Parse.zig:353)
==1589188==    by 0x24B4351: zig.Parse.parseRoot (Parse.zig:199)
==1589188==    by 0x24B17EE: zig.Ast.parse (Ast.zig:184)
==1589188==    by 0x2684083: Build.Step.Options.decltest.Options (Options.zig:682)
==1589188==    by 0x155656A: test_runner.mainTerminal (test_runner.zig:218)

==1589188== Use of uninitialised value of size 8
==1589188==    at 0x15550FF: heap.debug_allocator.DebugAllocator(.{ .stack_trace_frames = 10, .enable_memory_limit = false, .safety = true, .thread_safe = true, .MutexType = null, .never_unmap = false, .retain_metadata = false, .verbose_log = false, .backing_allocator_zeroes = true, .resize_stack_traces = true, .canary = 2824291834806075834, .page_size = 131072 }).free (debug_allocator.zig:937)
==1589188==    by 0x14F846B: rawFree (Allocator.zig:147)
==1589188==    by 0x14F846B: heap.arena_allocator.ArenaAllocator.deinit (arena_allocator.zig:60)
==1589188==    by 0x26840E9: Build.Step.Options.decltest.Options (Options.zig:536)
==1589188==    by 0x155656A: test_runner.mainTerminal (test_runner.zig:218)
==1589188==    by 0x1550791: test_runner.main (test_runner.zig:66)
==1589188==    by 0x154FF2D: callMain (start.zig:618)
==1589188==    by 0x154FF2D: callMainWithArgs (start.zig:587)
==1589188==    by 0x154FF2D: main (start.zig:602)


==1589188== Conditional jump or move depends on uninitialised value(s)
==1589188==    at 0x158A63C: testing.expectEqualSlices__anon_35769 (testing.zig:368)
==1589188==    by 0x2809019: os.linux.IoUring.test.ring mapped buffers recv (IoUring.zig:4194)
==1589188==    by 0x155656A: test_runner.mainTerminal (test_runner.zig:218)
==1589188==    by 0x1550791: test_runner.main (test_runner.zig:66)
==1589188==    by 0x154FF2D: callMain (start.zig:618)
==1589188==    by 0x154FF2D: callMainWithArgs (start.zig:587)
==1589188==    by 0x154FF2D: main (start.zig:602)

==1589188== Conditional jump or move depends on uninitialised value(s)
==1589188==    at 0x251F0E5: math.big.int.llaccum__anon_1297017 (int.zig:3611)
==1589188==    by 0x251BB84: math.big.int.llmulaccKaratsuba__anon_1296380 (int.zig:3531)
==1589188==    by 0x2513F3A: math.big.int.llmulacc__anon_1295371 (int.zig:3404)
==1589188==    by 0x286B34F: math.big.int.Mutable.mulWrapNoAlias (int.zig:875)
==1589188==    by 0x286ADEA: math.big.int.Managed.mulWrap (int.zig:3122)
==1589188==    by 0x286E490: math.big.int_test.test.mulWrap large (int_test.zig:1549)
==1589188==    by 0x155656A: test_runner.mainTerminal (test_runner.zig:218)
==1589188==    by 0x1550791: test_runner.main (test_runner.zig:66)
==1589188==    by 0x154FF2D: callMain (start.zig:618)
==1589188==    by 0x154FF2D: callMainWithArgs (start.zig:587)
==1589188==    by 0x154FF2D: main (start.zig:602)

[RichardMarto]

Hey guys, this seems like something I could help with, feel free to assign it to me, I'll take a better look in the meantime.