Editing Memory management (section)

==== Stack allocation ====
{{main|Stack-based memory allocation}}
Many [[Unix-like]] systems as well as [[Microsoft Windows]] implement a function called {{code|alloca}} for dynamically allocating stack memory in a way similar to the heap-based {{code|malloc}}. A compiler typically translates it to inlined instructions manipulating the stack pointer.<ref>{{man|3|alloca|Linux}}</ref> Although there is no need of manually freeing memory allocated this way as it is automatically freed when the function that called {{code|alloca}} returns, there exists a risk of overflow. And since alloca is an ''ad hoc'' expansion seen in many systems but never in POSIX or the C standard, its behavior in case of a stack overflow is undefined.

A safer version of alloca called {{code|_malloca}}, which reports errors, exists on Microsoft Windows. It requires the use of {{code|_freea}}.<ref>{{cite web |title=_malloca |url=https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/malloca?view=vs-2019 |website=Microsoft CRT Documentation | date=26 October 2022 |language=en-us}}</ref> [[gnulib]] provides an equivalent interface, albeit instead of throwing an SEH exception on overflow, it delegates to malloc when an overlarge size is detected.<ref>{{cite web |title=gnulib/malloca.h |url=https://github.com/coreutils/gnulib/blob/master/lib/malloca.h |website=GitHub |access-date=24 November 2019}}</ref> A similar feature can be emulated using manual accounting and size-checking, such as in the uses of {{code|alloca_account}} in glibc.<ref>{{cite web |title=glibc/include/alloca.h |url=https://github.com/bminor/glibc/blob/780684eb04298977bc411ebca1eadeeba4877833/include/alloca.h |publisher=Beren Minor's Mirrors |date=23 November 2019}}</ref>