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c++compilationmallocheap-memory
SRobertJames
SRobertJames

Reputation: 9206

How do C++ compilers handle malloc failures during new operator?

C++ compilers implement new Obj as a wrapper to malloc(sizeof(Obj)). But malloc can fail! What code do C++ compilers insert to handle the failures, and what does it do?

Upvotes: 0

Views: 63

Answers (1)

eerorika
eerorika

Reputation: 238351

C++ standard says about the behaviour:

[basic.stc.dynamic.allocation]

An allocation function that has a non-throwing exception specification ([except.spec]) indicates failure by returning a null pointer value. Any other allocation function never returns a null pointer value and indicates failure only by throwing an exception ([except.throw]) of a type that would match a handler ([except.handle]) of type std​::​bad_alloc ([bad.alloc]).

In the non-throwing case, there is no handling needed because returning null is exactly how malloc signifies failure.

In the throwing case, a language implementation that wraps malloc has to check whether the allocation was successful, and throw if it wasn't.

Upvotes: 2

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