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 if file is a
not_actual_file_p.
(not_actual_file_p): Return true if file is /dev/zero as well.
* doc/invoke.texi: Update -dumpdir documentation.
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 | 3 ++-
gcc/gcc.c | 6 ++++--
gcc/testsuite/gcc.dg/devnull-dump.c | 7 +++++++
3 files changed, 13 insertions(+), 3 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..4a17cd4d317 100644
--- a/gcc/doc/invoke.texi
+++ b/gcc/doc/invoke.texi
@@ -1877,7 +1877,8 @@ 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 the output
+file is a special file like @code{/dev/null}. 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..43d7cde1be9 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -5098,7 +5098,8 @@ process_command (unsigned int decoded_options_count,
bool explicit_dumpdir = dumpdir;
- if (!save_temps_overrides_dumpdir && explicit_dumpdir)
+ if ((!save_temps_overrides_dumpdir && explicit_dumpdir)
+ || (output_file && not_actual_file_p (output_file)))
{
/* Do nothing. */
}
@@ -10716,7 +10717,8 @@ static bool
not_actual_file_p (const char *name)
{
return (strcmp (name, "-") == 0
- || strcmp (name, HOST_BIT_BUCKET) == 0);
+ || strcmp (name, HOST_BIT_BUCKET) == 0
+ || strcmp (name, "/dev/zero") == 0);
}
/* %:dumps spec function. Take an optional argument that overrides
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
