Member Avatar for ayeshashahid

i have a serious problem with this malloc function used in C language.i have been studying the topic "new" for few days,and there i found a code in which malloc was used.i am trying to change it to new but my compiler always always CRASHES.

the line which i think crashes my compiler is:-

r->next=(class polynomial *)malloc(sizeof(class polynomial))

if somebody wants the program which put me in trouble,please do ask for it.

please please help me im in a big trouble.

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Good that switching to the C++ allocator fixed the crash — that’s exactly where these problems usually come from. The C malloc family hands you raw bytes (no object setup), while a C++ new expression both obtains storage and initializes the object you requested; using the wrong one can leave members, vtables or invariants uninitialized. (docs.cppreference.com)

Also keep in mind the allocation/deallocation rules: memory obtained with new must be released with the matching delete form, and memory from malloc/calloc/realloc must be freed with free. Mixing those (or using the wrong form for arrays) is undefined behavior and a frequent source of crashes — the FAQ and reference documents warn strongly about this. ’s point about the cast syntax was a good prompt to tidy up the code style (C-style casts are unnecessary here). (isocpp.org)

For debugging pointers like r (as suggested): build with debug info and runtime checks, use AddressSanitizer or Valgrind to catch use-after-free and invalid access, and prefer RAII to avoid manual errors. Replacing raw new/delete with smart pointers keeps ownership explicit and prevents leaks. Example pattern for a linked node: 

struct Node {
    std::unique_ptr<Node> next;
    // data members...
};

auto n = std::make_unique<Node>();
n->next = std::make_unique<Node>();

Use smart pointers where ownership is clear. (clang.llvm.org)

If you must work with raw buffers (rare in typical code), allocate bytes with malloc/aligned_alloc and then construct objects into that storage with placement new, and remember to call destructors manually — this is advanced, error-prone work and alignment matters for over‑aligned types. (en.cppreference.com)

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Member Avatar for Greywolf333

i have a serious problem with this malloc function used in C language.i have been studying the topic "new" for few days,and there i found a code in which malloc was used.i am trying to change it to new but my compiler always always CRASHES.

the line which i think crashes my compiler is:-

r->next=(class polynomial *)malloc(sizeof(class polynomial))

if somebody wants the program which put me in trouble,please do ask for it.

please please help me im in a big trouble.

First is (class polynomial *) even correct? Shouldn't it just be (polynomial*)? If it is possible to do it your "class" way, then nevermind this part.

malloc should only be used for primitive types that do not require a constructor because malloc will not call the constructor. So even though that code may compile, it will not use your constructor that you have specified in your polynomial class. Therefore your program may crash because your constructor is necessary for your program to function properly.

You definitely should use the "new" operator, because "new" calls the constructor during allocation. The correct syntax would be:

r->next = new polynomial;

Member Avatar for Ancient Dragon

I don't ever use malloc() in a c++ program, its just too confusing to mix malloc() and new together in the same c++ program. Stick with new for consistency and to be less error prone.

Member Avatar for Tumlee

Are you sure it's your *compiler* that's crashing? Or is your program crashing during execution? If it's the latter, it's more than likely that "r" is pointing to invalid memory or "r" is a NULL pointer.

Member Avatar for ayeshashahid

the error was with the "malloc",i finally changed it to "new" with some changes in my code too.well thanks everyone for your help, appreciate it :)

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