Re: [PATCH v2 1/2] t: add "test-tool genbytes" to avoid slow tr(1) on macOS

[Junio C Hamano <gitster@pobox.com>]

"Kristofer Karlsson via GitGitGadget" <gitgitgadget@gmail.com>
writes:

> diff --git a/t/helper/test-genbytes.c b/t/helper/test-genbytes.c
> new file mode 100644
> index 0000000000..b760326b24
> --- /dev/null
> +++ b/t/helper/test-genbytes.c
> @@ -0,0 +1,61 @@
> +#define DISABLE_SIGN_COMPARE_WARNINGS
> +
> +#include "test-tool.h"
> +#include "git-compat-util.h"
> +#include "hex-ll.h"
> +
> +/*
> + * Write "count" copies of "byte" to stdout, or an endless stream of them if
> + * "count" is negative.
> + */
> +static int generate_bytes(char byte, intmax_t count)
> +{
> +	char buf[256 * 1024];

Allocating 256kB on stack may not be a great practice, but this may
sufficiently work on most reasonable systems, as this is an internal
of a "run once and exit" test helper function.

Still, the stack memory for the primary thread of a process is
limited to 8MB or so on modern Linux systems, and I hear macOS also
uses 8MB.  I am not familiar with Windows, but some documentation
found on the Web seems to say that their linker gives 1MB to their
product by default, and among 1MB, 256kB is not an insignificant
fraction.

Again, this is an internal of a "run once and exit" test helper, so
declaring this as "static char buf[]" should not pose an issue; it is
not like you would need to have multiple simultaneous invocations of
this function, each of which needs to fill this buffer with
different values.