The `configure` scripts generated with autoconf often tests compiler
features by setting output to `/dev/null`, which then sets the dump
folder as being /dev/* and the compilation halts with an error because
GCC cannot create files in /dev/. This is a problem when configure is
testing for compiler features because it cannot tell if the failure was
due to unsupported features or any other problem, and disable it even
if it is working.
As an example, running configure overriding CFLAGS="-fdump-ipa-clones"
will result in several compiler-features as being disabled because of
gcc halting with an error creating files in /dev/*.
This commit fixes this issue by checking if the output file is
/dev/null or /dev/zero. In this case we use the current working
directory for dump output instead of the directory of the output
file because we cannot write to /dev/*.
gcc/ChangeLog
2021-11-16 Giuliano Belinassi <gbelina...@suse.de>
* gcc.c (process_command): Skip dumpdir override on -o /dev/null
or -o /dev/zero.
gcc/testsuite/ChangeLog
2021-11-16 Giuliano Belinassi <gbelina...@suse.de>
* gcc.dg/devnull-dump.c: New.
Signed-off-by: Giuliano Belinassi <gbelina...@suse.de>
---
gcc/doc/invoke.texi | 4 +++-
gcc/gcc.c | 19 +++++++++++++++----
gcc/testsuite/gcc.dg/devnull-dump.c | 7 +++++++
3 files changed, 25 insertions(+), 5 deletions(-)
create mode 100644 gcc/testsuite/gcc.dg/devnull-dump.c
diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi
index 6070288856c..4c056606e0c 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1877,7 +1877,9 @@ named @file{dir/bar.*}, combining the given @var{dumppfx}
with the
default @var{dumpbase} derived from the primary output name. Dump
outputs also take the input name suffix: @file{dir/bar.c.*}.
-It defaults to the location of the output file; options
+It defaults to the location of the output file, unless @option{-o /dev/null}
+or @option{-o /dev/zero} is passed to the compiler: on those cases the
@option{cwd}
+will be used instead. Options
@option{-save-temps=cwd} and @option{-save-temps=obj} override this
default, just like an explicit @option{-dumpdir} option. In case
multiple such options are given, the last one prevails:
diff --git a/gcc/gcc.c b/gcc/gcc.c
index 506c2acc282..0173018ac04 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -5109,10 +5109,21 @@ process_command (unsigned int decoded_options_count,
{
free (dumpdir);
dumpdir = NULL;
- temp = lbasename (output_file);
- if (temp != output_file)
- dumpdir = xstrndup (output_file,
- strlen (output_file) - strlen (temp));
+ if (strcmp(output_file, "/dev/null") == 0
+ || strcmp(output_file, "/dev/zero") == 0)
+ {
+ /* If output is /dev/null or /dev/zero, we cannot set the dumpdir to
+ /dev/ because no files can be created on that directory. In this
+ case, we do nothing. */
+ }
+ else
+ {
+ /* Set dumpdir as being the same directory where the output file is.
*/
+ temp = lbasename (output_file);
+ if (temp != output_file)
+ dumpdir = xstrndup (output_file,
+ strlen (output_file) - strlen (temp));
+ }
}
else if (dumpdir)
{
diff --git a/gcc/testsuite/gcc.dg/devnull-dump.c
b/gcc/testsuite/gcc.dg/devnull-dump.c
new file mode 100644
index 00000000000..378e0901c28
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/devnull-dump.c
@@ -0,0 +1,7 @@
+/* { dg-do assemble } */
+/* { dg-options "-fdump-ipa-clones -o /dev/null" } */
+
+int main()
+{
+ return 0;
+}
--
2.33.1
