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While I'm wearing my Valgrind hat, memcheck detects a few issues in the regression tests tlm/bus_dmi systemc/misc/user_guide/chpt4.4 systemc/datatypes/misc/concat/test07 I haven't looked at the first two. For the last one, here is a cut down version that reproduces the first error. #include "systemc.h" #include "valgrind/memcheck.h" void checkout( const sc_unsigned* actual_p, const sc_unsigned* expected_p ) { cout << *actual_p <<" " << *expected_p << endl; cout <<"another line" << endl; } int sc_main(int argc, char* argv[]) { int high_i = 64; int low_i = 30; sc_int_base high_int(high_i); sc_int_base low_int(low_i); sc_signed low_signed(low_i); low_int = "0x0000000000000000"; low_signed = "0x0000000000000000"; high_int = "0xffffffffffffffff"; cout << endl << dec << "[" << high_i << "," << low_i << "]:" << endl; cout << hex << " int " << (high_int,low_int) << " <- ( " << high_int << " , " << low_int << " )" << endl; const sc_unsigned* actual_p = &(high_int,low_signed).value(); { int i; std::vector<int> bits(actual_p->nbits/32+1); VALGRIND_GET_VBITS(actual_p->digit,bits.data(),actual_p->nbits/8+1); std::cout << "actual bits "; for (auto b : bits) { std::cout << b << " "; } std::cout << std::endl; } const sc_unsigned* expected_p = &(high_int,low_int).value(); if ( *actual_p != *expected_p ) { checkout(actual_p, expected_p); cout << "!!! ERROR (high_int,low_signed):" << endl; cout << " expected: " << hex << *expected_p << endl; cout << " actual: " << hex << *actual_p << endl; cout << " diff mask: " << hex << ((high_int,low_int) ^ (high_int,low_signed)) << endl; } cout << "Program completed" << endl; return 0; } A couple of things to note: I hacked the definition of sc_unsigned to make digit and nbits public so that I could access them directly. This won't compile without that change. I've added a print of Valgrind's vbits (which tells which bits have been initialized and which are uninitialized). The output is as follows 64,30]: int 3fffffffffffffffc0000000 <- ( ffffffffffffffff , 00000000 ) actual bits c0000000 0 0 ==6726== Conditional jump or move depends on uninitialised value(s) ==6726== at 0x4A1081B: sc_dt::vec_cmp(int, unsigned int const*, int, unsigned int const*) (src/sysc/datatypes/int/sc_nbutils.h:427) ==6726== by 0x4A2B106: sc_dt::vec_skip_and_cmp(int, unsigned int const*, int, unsigned int const*) (src/sysc/datatypes/int/sc_nbutils.h:500) ==6726== by 0x4A37DE0: sc_dt::compare_unsigned(int, int, int, unsigned int const*, int, int, int, unsigned int const*, int, int) (src/sysc/datatypes/int/sc_unsigned.cpp:2026) ==6726== by 0x4A37D57: sc_dt::operator==(sc_dt::sc_unsigned const&, sc_dt::sc_unsigned const&) (src/sysc/datatypes/int/sc_unsigned.cpp:1719) ==6726== by 0x4A3BEAC: sc_dt::operator!=(sc_dt::sc_unsigned const&, sc_dt::sc_unsigned const&) (src/sysc/datatypes/int/sc_nbcommon.inc:1930) ==6726== by 0x2059E3: sc_main (small.cpp:97) ==6726== by 0x4A4C579: sc_elab_and_sim (src/sysc/kernel/sc_main_main.cpp:89) ==6726== by 0x4A4C3E1: main (src/sysc/kernel/sc_main.cpp:36) ==6726== Uninitialised value was created by a heap allocation ==6726== at 0x4853224: operator new[](unsigned long) (vg_replace_malloc.c:477) ==6726== by 0x4A419DA: sc_core::sc_byte_heap::initialize(unsigned long) (src/sysc/utils/sc_temporary.h:96) ==6726== by 0x4A41406: sc_core::sc_byte_heap::sc_byte_heap(unsigned long) (src/sysc/utils/sc_temporary.h:114) ==6726== by 0x4A40C94: __cxx_global_var_init (src/sysc/datatypes/misc/sc_concatref.cpp:55) ==6726== by 0x4A40D48: _GLOBAL__sub_I_sc_concatref.cpp (sc_concatref.cpp:0) ==6726== by 0x400D2FC: ??? (in /libexec/ld-elf.so.1) ==6726== by 0x400C03C: ??? (in /libexec/ld-elf.so.1) ==6726== by 0x40098C8: ??? (in /libexec/ld-elf.so.1) The first nibble of the vbits is 'c', meaning that the top two bits are uninitialized. That makes some sense as the value is '3fff..' which has the inverse pattern, 0011 binary. Interestingly, this is one case where Valgrind detects an error that ASAN does not - ASAN has only byte level granularity, so it cannot detect cases where only part of a byte is uninitialized. That is as far as I've gotten so far. No idea yet if the issue is in 'operator,' or in 'value()'.