On Tue, Mar 26, 2024 at 11:37 PM Peter Damianov <peter0...@disroot.org> wrote:
>
> lto-wrapper generates Makefiles that use the following:
> touch -r file file.tmp && mv file.tmp file
> to truncate files.
> If there is no suitable "touch" or "mv" available, then this errors with
> "The system cannot find the file specified".
>
> The solution here is to check if sh -c true works, before trying to use it in
> the Makefile. If it doesn't, then fall back to "copy /y nul file" instead.
> The fallback doesn't work exactly the same (the modified time of the file gets
> updated), but this doesn't seem to matter in practice.
I suppose it doesn't matter as we (no longer?) have the input as dependency
on the rule so make doesn't get confused to re-build it. I guess we
only truncate
the file because it's going to be deleted by another process.
Instead of doing sth like sh_exists I would suggest to simply use #ifdef __WIN
or something like that? Not sure if we have suitable macros to identify the
host operating system though and whether mingw, cygwin, etc. behave the same
here.
As a stop-gap solution doing
( @-touch -r ... ) || true
might also work? Or another way to note to make the command can fail
without causing a problem.
Another way would be to have a portable solution to truncate a file
(maybe even removing it would work). I don't think we should override
SHELL.
Richard.
> I tested this both in environments both with and without sh present, and
> observed no issues.
>
> Signed-off-by: Peter Damianov <peter0...@disroot.org>
> ---
> gcc/lto-wrapper.cc | 35 ++++++++++++++++++++++++++++++++---
> 1 file changed, 32 insertions(+), 3 deletions(-)
>
> diff --git a/gcc/lto-wrapper.cc b/gcc/lto-wrapper.cc
> index 5186d040ce0..8dee0aaa2d8 100644
> --- a/gcc/lto-wrapper.cc
> +++ b/gcc/lto-wrapper.cc
> @@ -1389,6 +1389,27 @@ make_exists (void)
> return errmsg == NULL && exit_status == 0 && err == 0;
> }
>
> +/* Test that an sh command is present and working, return true if so.
> + This is only relevant for windows hosts, where a /bin/sh shell cannot
> + be assumed to exist. */
> +
> +static bool
> +sh_exists (void)
> +{
> + const char *sh = "sh";
> + const char *sh_args[] = {sh, "-c", "true", NULL};
> +#ifdef _WIN32
> + int exit_status = 0;
> + int err = 0;
> + const char *errmsg
> + = pex_one (PEX_SEARCH, sh_args[0], CONST_CAST (char **, sh_args),
> + "sh", NULL, NULL, &exit_status, &err);
> + return errmsg == NULL && exit_status == 0 && err == 0;
> +#else
> + return true;
> +#endif
> +}
> +
> /* Execute gcc. ARGC is the number of arguments. ARGV contains the
> arguments. */
>
> static void
> @@ -1402,6 +1423,7 @@ run_gcc (unsigned argc, char *argv[])
> const char *collect_gcc;
> char *collect_gcc_options;
> int parallel = 0;
> + bool have_sh = sh_exists ();
> int jobserver = 0;
> bool jobserver_requested = false;
> int auto_parallel = 0;
> @@ -2016,6 +2038,7 @@ cont:
> argv_ptr[5] = NULL;
> if (parallel)
> {
> + fprintf (mstream, "SHELL=%s\n", have_sh ? "sh" : "cmd");
> fprintf (mstream, "%s:\n\t@%s ", output_name, new_argv[0]);
> for (j = 1; new_argv[j] != NULL; ++j)
> fprintf (mstream, " '%s'", new_argv[j]);
> @@ -2024,9 +2047,15 @@ cont:
> truncate them as soon as we have processed it. This
> reduces temporary disk-space usage. */
> if (! save_temps)
> - fprintf (mstream, "\t@-touch -r \"%s\" \"%s.tem\" > /dev/null
> "
> - "2>&1 && mv \"%s.tem\" \"%s\"\n",
> - input_name, input_name, input_name, input_name);
> + {
> + fprintf (mstream,
> + have_sh
> + ? "\t@-touch -r \"%s\" \"%s.tem\" > /dev/null "
> + "2>&1 && mv \"%s.tem\" \"%s\"\n"
> + : "\t@-copy /y nul \"%s\" > NUL "
> + "2>&1\n",
> + input_name, input_name, input_name, input_name);
> + }
> }
> else
> {
> --
> 2.39.2
>
