My approach for this specific problem is to use a compiler that warns about unused return value, such as gcc or clang. I know that stdlib.h on Linux and Mac OS X already decorates realloc() with warn_unused_result attribute.
But just naively setting p = realloc(p, ...) is also wrong, since if the allocation fails, p would be set to NULL but the original object is still allocated. The original pointer is lost and now a memory leak. Use reallocf() which frees the original memory if it could not be resized.
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@liulk
Ha, I completely forgot to mention Clang! It does indeed have the best warnings of any compiler I've used. I almost always compile with -Wall -Wextra -Wpedantic -Werror; that last one (as you know, although the reader might not) causes the build to fail on any warnings.
I also use cppcheck as part of my autoreview workflow, and resolve all linter warnings before committing to the production branch.
@codevault
You're right, reallocf() would just free the memory and cause data loss, so it would serve a different use case than realloc(). The more general solution would be to always use this pattern, which is more verbose:
void*q=realloc(p,new_size);if(q==NULL){// do error handling.return;}p=q;
I just find that in most of my use cases, I would end up freeing p in the error handling, so I would just use reallocf() which results in less verbose code.
Thank you for stopping by! I am a full-stack developer that combines the power of entrepreneurship and programming to make the lives of programmers easier.
My approach for this specific problem is to use a compiler that warns about unused return value, such as gcc or clang. I know that stdlib.h on Linux and Mac OS X already decorates realloc() with warn_unused_result attribute.
stackoverflow.com/a/2889601
But just naively setting
p = realloc(p, ...)is also wrong, since if the allocation fails, p would be set toNULLbut the original object is still allocated. The original pointer is lost and now a memory leak. Use reallocf() which frees the original memory if it could not be resized.That's a really nice feature, didn't know about it.
But wouldn't that mean data loss in case the memory can't be resized? Wouldn't that become an unrecoverable error?
@liulk Ha, I completely forgot to mention Clang! It does indeed have the best warnings of any compiler I've used. I almost always compile with
-Wall -Wextra -Wpedantic -Werror; that last one (as you know, although the reader might not) causes the build to fail on any warnings.I also use
cppcheckas part of my autoreview workflow, and resolve all linter warnings before committing to the production branch.@codevault You're right, reallocf() would just free the memory and cause data loss, so it would serve a different use case than realloc(). The more general solution would be to always use this pattern, which is more verbose:
I just find that in most of my use cases, I would end up freeing p in the error handling, so I would just use reallocf() which results in less verbose code.
I see, that makes sense. I can see myself freeing the memory most of the time when reallocation fails.
Good to note. Thanks!