Old C code declared variables at the beginning of a function because it made compilers easier to implement, in a single pass. If you interleave variables and statements, then calculating the amount of stack space needed for the function call requires multiple passes. Knowing this, defenses of "variables at the top" often seem like rationalizations to me.
There's a reason that other programming languages don't share this convention, and that's because compilers had evolved enough in sophistication to allow interleaved variables and statements from their beginnings; and they had no legacy code bases anchoring their code style, like C does.
Declaring variables at the top is suboptimal compared to declaring them at their usage. It requires less working memory to understand, and it's fewer lines of code, and the resulting code can often be easier to understand due to context. Standalone variables typically either require more documentation to make sense, or else they don't make sense until you see them used in context.
The C language has a lot of bad conventions and semantics that have led to thousands of bugs over the years. Variables whose scope span entire functions is one of them. There's no articulable advantage and the downside is greater demands on working memory, and greater risk of defects (variables being visible before they're initialized or outside places where they make sense). Rust is on the right track allowing variable lifetimes to be defined and managed in a precise way.
Old C code declared variables at the beginning of a function because it made compilers easier to implement, in a single pass. If you interleave variables and statements, then calculating the amount of stack space needed for the function call requires multiple passes. Knowing this, defenses of "variables at the top" often seem like rationalizations to me.
There's a reason that other programming languages don't share this convention, and that's because compilers had evolved enough in sophistication to allow interleaved variables and statements from their beginnings; and they had no legacy code bases anchoring their code style, like C does.
Declaring variables at the top is suboptimal compared to declaring them at their usage. It requires less working memory to understand, and it's fewer lines of code, and the resulting code can often be easier to understand due to context. Standalone variables typically either require more documentation to make sense, or else they don't make sense until you see them used in context.
The C language has a lot of bad conventions and semantics that have led to thousands of bugs over the years. Variables whose scope span entire functions is one of them. There's no articulable advantage and the downside is greater demands on working memory, and greater risk of defects (variables being visible before they're initialized or outside places where they make sense). Rust is on the right track allowing variable lifetimes to be defined and managed in a precise way.