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List:       kde-bugs-dist
Subject:    [valgrind] [Bug 392855] valgrind reports 1 additional allocation and 1024 additional bytes allocated
From:       David Rankin <bugzilla_noreply () kde ! org>
Date:       2018-05-02 2:55:10
Message-ID: bug-392855-17878-JYnfkIU50C () http ! bugs ! kde ! org/
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https://bugs.kde.org/show_bug.cgi?id=392855

David Rankin <drankinatty@suddenlinkmail.com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
         Resolution|INVALID                     |---

--- Comment #5 from David Rankin <drankinatty@suddenlinkmail.com> ---
But that is what I'm saying, with gcc 7.3 it is still broken with -O0, e.g.

$ gcc -S -O0 -o vgtest_noopt.asm vgtest2.c

$ cat vgtest_noopt.asm
        .file   "vgtest2.c"
        .text
        .section        .rodata
.LC0:
        .string "a: %d\n"
        .text
        .globl  main
        .type   main, @function
main:
.LFB5:
        .cfi_startproc
        pushq   %rbp
        .cfi_def_cfa_offset 16
        .cfi_offset 6, -16
        movq    %rsp, %rbp
        .cfi_def_cfa_register 6
        subq    $16, %rsp
        movl    $4, %edi
        call    malloc@PLT
        movq    %rax, -8(%rbp)
        movq    -8(%rbp), %rax
        movl    $5, (%rax)
        movq    -8(%rbp), %rax
        movl    (%rax), %eax
        movl    %eax, %esi
        leaq    .LC0(%rip), %rdi
        movl    $0, %eax
        call    printf@PLT
        movq    -8(%rbp), %rax
        movq    %rax, %rdi
        call    free@PLT
        movl    $0, %eax
        leave
        .cfi_def_cfa 7, 8
        ret
        .cfi_endproc
.LFE5:
        .size   main, .-main
        .ident  "GCC: (GNU) 7.3.1 20180406"
        .section        .note.GNU-stack,"",@progbits

valgrind still reports the wrong memory allocation. This time 1028-bytes
(showing the 4-bytes allocated for the int, but a magic 1024 more)

$ valgrind ./bin/vgtest_noopt
==17950== Memcheck, a memory error detector
==17950== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==17950== Using Valgrind-3.13.0 and LibVEX; rerun with -h for copyright info
==17950== Command: ./bin/vgtest_noopt
==17950==
a: 5
==17950==
==17950== HEAP SUMMARY:
==17950==     in use at exit: 0 bytes in 0 blocks
==17950==   total heap usage: 2 allocs, 2 frees, 1,028 bytes allocated
==17950==
==17950== All heap blocks were freed -- no leaks are possible
==17950==
==17950== For counts of detected and suppressed errors, rerun with: -v
==17950== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 0 from 0)

Thank you for looking at this.

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