Create array at runtime

[Joseph Hesse]

I am surprised that the following compiles with g++.

void f(int x)
{
int a[x];
}

I thought that the size of such an array had to be known at compile time
and couldn't be created at run time? Is this a new feature?
Thank you,
Joe

[Rick C. Hodgin]

GCC has allowed VLA's in C++ for a while:

https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html

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Rick C. Hodgin | http://www.libsf.org/ | http://tinyurl.com/yaogvqhj
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[red floyd]

On 9/29/2017 10:12 AM, Stefan Ram wrote:

> Joseph Hesse <jo...@gmail.com> writes:
>> I am surprised that the following compiles with g++.
>> void f(int x)
>> {
>> int a[x];
>> }
>

> This might be a compiler-specific extension.
>
> Maybe you would like to try:
>
> -std=c++14 -pedantic -pedantic-errors

Isn't that a C99-ism?

[bitrex]

On 09/29/2017 01:12 PM, Stefan Ram wrote:
> Joseph Hesse <jo...@gmail.com> writes:

>> I am surprised that the following compiles with g++.
>> void f(int x)
>> {
>> int a[x];
>> }
>

> This might be a compiler-specific extension.
>
> Maybe you would like to try:
>
> -std=c++14 -pedantic -pedantic-errors

It compiles OK with -std=C++98 for all versions of gcc for x86-64 over
4.4.7; the -pedantic flag gives the warning "ISO C++ forbids variable
length arrays." Clang 3.0 and above for x86-64 it also compiles but
warns "variable length arrays are a C99 feature, accepted as extension"
with -std=C++98 -pedantic; with -std=C++14 -pedantic for clang 3.5 and
above it just reports "variable length arrays are a C99 feature"