Valgrind - Conditional jump or move depends on uninitialised value(s)

[romintomasetti]

I ran Valgrind on my program, that at some point uses miniz-cpp.

It raised one error for miniz-cpp, which is the following:

==37967== Conditional jump or move depends on uninitialised value(s)
==37967==    at 0x565D9C4: tdefl_find_match (zip_file.hpp:2339)
==37967==    by 0x565D9C4: tdefl_compress_normal (zip_file.hpp:2610)
==37967==    by 0x565EA34: tdefl_compress (zip_file.hpp:2727)
==37967==    by 0x565EBDE: tdefl_compress_buffer (zip_file.hpp:2747)
==37967==    by 0x566506B: mz_zip_writer_add_mem_ex (zip_file.hpp:4430)
==37967==    by 0x5663B0F: mz_zip_writer_add_mem (zip_file.hpp:4190)
==37967==    by 0x566E63D: miniz_cpp::zip_file::writestr(std::string const&, std::string const&) (zip_file.hpp:5514)
==37967==    by 0x566E515: miniz_cpp::zip_file::write(std::string const&, std::string const&) (zip_file.hpp:5504)

I don't think I have the latest code of miniz-cpp so I also put the line here:

    }
    if (!dist) break; q = (const mz_uint16*)(d->m_dict + probe_pos); if (TDEFL_READ_UNALIGNED_WORD(q) != s01) continue; p = s; probe_len = 32;
    do { } while ( (TDEFL_READ_UNALIGNED_WORD(++p) == TDEFL_READ_UNALIGNED_WORD(++q)) && (TDEFL_READ_UNALIGNED_WORD(++p) == TDEFL_READ_UNALIGNED_WORD(++q)) &&
                   (TDEFL_READ_UNALIGNED_WORD(++p) == TDEFL_READ_UNALIGNED_WORD(++q)) && (TDEFL_READ_UNALIGNED_WORD(++p) == TDEFL_READ_UNALIGNED_WORD(++q)) && (--probe_len > 0) );
    if (!probe_len)
    {

Tracking the origin gives:

==44853== Conditional jump or move depends on uninitialised value(s)
==44853==    at 0x564B8A2: tdefl_find_match (zip_file.hpp:2338)
==44853==    by 0x564B8A2: tdefl_compress_normal (zip_file.hpp:2610)
==44853==    by 0x564C8F5: tdefl_compress (zip_file.hpp:2727)
==44853==    by 0x564CA9F: tdefl_compress_buffer (zip_file.hpp:2747)
==44853==    by 0x5652F2C: mz_zip_writer_add_mem_ex (zip_file.hpp:4430)
==44853==    by 0x56519D0: mz_zip_writer_add_mem (zip_file.hpp:4190)
==44853==    by 0x565C4FF: miniz_cpp::zip_file::writestr(std::string const&, std::string const&) (zip_file.hpp:5514)
==44853==    by 0x565C3D7: miniz_cpp::zip_file::write(std::string const&, std::string const&) (zip_file.hpp:5504)
...
==44853==  Uninitialised value was created by a heap allocation
==44853==    at 0x4A37ECB: malloc (vg_replace_malloc.c:307)
==44853==    by 0x56422AB: def_alloc_func (zip_file.hpp:1054)
==44853==    by 0x5652C34: mz_zip_writer_add_mem_ex (zip_file.hpp:4375)
==44853==    by 0x56519D0: mz_zip_writer_add_mem (zip_file.hpp:4190)
==44853==    by 0x565C4FF: miniz_cpp::zip_file::writestr(std::string const&, std::string const&) (zip_file.hpp:5514)
==44853==    by 0x565C3D7: miniz_cpp::zip_file::write(std::string const&, std::string const&) (zip_file.hpp:5504)
...
==44853== 

It would be great if you can solve this issue 😄

[tfussell]

Thanks for the issue. I'll try to take care of this soon.

[romintomasetti]

Thanks ! I think that using calloc instead of malloc in def_alloc_func would already solve some issues 😄