Communities

Writing
Writing
Codidact Meta
Codidact Meta
The Great Outdoors
The Great Outdoors
Photography & Video
Photography & Video
Scientific Speculation
Scientific Speculation
Cooking
Cooking
Electrical Engineering
Electrical Engineering
Judaism
Judaism
Languages & Linguistics
Languages & Linguistics
Software Development
Software Development
Mathematics
Mathematics
Christianity
Christianity
Code Golf
Code Golf
Music
Music
Physics
Physics
Linux Systems
Linux Systems
Power Users
Power Users
Tabletop RPGs
Tabletop RPGs
Community Proposals
Community Proposals
tag:snake search within a tag
answers:0 unanswered questions
user:xxxx search by author id
score:0.5 posts with 0.5+ score
"snake oil" exact phrase
votes:4 posts with 4+ votes
created:<1w created < 1 week ago
post_type:xxxx type of post
Search help
Notifications
Mark all as read See all your notifications »
Q&A

Welcome to Software Development on Codidact!

Will you help us build our independent community of developers helping developers? We're small and trying to grow. We welcome questions about all aspects of software development, from design to code to QA and more. Got questions? Got answers? Got code you'd like someone to review? Please join us.

Comments on How to declare variable-length arrays correctly?

Post

How to declare variable-length arrays correctly?

+8
−0

This is meant as a FAQ Q&A regarding variable-length arrays (VLA). The two bugs described below are surprisingly common.


I'm trying to use the variable-length arrays feature of C99 (and newer) but I'm facing problems with it.

  • Whenever I write a program like this, I get strange crashes and unexpected behavior:

    int size;
    int array[size];
    scanf("%d", &size);
    
  • Similarly, I also get crashes and strange behavior when I do this:

    int size = 1000000;
    ...
    int array[size]; 
    
History
Why does this post require moderator attention?
You might want to add some details to your flag.
Why should this post be closed?

1 comment thread

Shouldn't the first example result in uninitialized variable warning? (2 comments)
Shouldn't the first example result in uninitialized variable warning?
Olin Lathrop‭ wrote about 2 years ago

Shouldn't the first example result in uninitialized variable warning?

Lundin‭ wrote about 2 years ago

Olin Lathrop‭ If you are lucky then yes. With gcc you have to do -Wall to enable the warning for example.