[PATCH 0/1] MR3797: makedep: Make *.tab.c build stable in parallel makes.

[Akihiro Sagawa (＠sgwaki)]

In `Makefile`, `foobar.tab.c` is made from the following rules:
```
foobar.tab.h: foobar.y
       bison -o foobar.tab.c -d foobar.y ---- Rule X
foobar.tab.c: foobar.y foobar.tab.h
       bison -o $@ foobar.y --- Rule Y
```
Normally, `Rule X` is used. In parallel makes, if `foobar.tab.c` is
considered while updating `foobar.tab.h` by `Rule X`, `Rule Y` is used.
So, if we compare build directories, there might be a difference in that
`foobar.tab.c` may or may not contain `#include "foobar.tab.h"`.

To avoid the above situation, this patch introduces [Grouped Targets](https://www.gnu.org/software/make/manual/html_node/Multiple-Targets.html#ind...) which is
new in GNU Make 4.3.

The previous rules still apply to prevent build failures on older
systems, such as Ubuntu 20.04 LTS.

[PATCH 1/1] makedep: Make *.tab.c build stable in parallel makes.

[Akihiro Sagawa]

From: Akihiro Sagawa

In Makefile, foobar.tab.c is made from the following rules:
---
foobar.tab.h: foobar.y
       bison -o foobar.tab.c -d foobar.y ---- Rule X
foobar.tab.c: foobar.y foobar.tab.h
       bison -o $@ foobar.y --- Rule Y
---
Normally, Rule X is used. In parallel makes, if foobar.tab.c is
considered while updating foobar.tab.h by Rule X, Rule Y is used.
So, if we compare build directories, there might be a difference in
that foobar.tab.c may or may not contain #include "foobar.tab.h".

To avoid the above situation, this patch introduces Grouped Targets
which is new in GNU Make 4.3.

The previous rules still apply to prevent build failures on older
systems, such as Ubuntu 20.04 LTS.
---
 tools/makedep.c | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/tools/makedep.c b/tools/makedep.c
index 8495d93d8c6..2b6e36e6196 100644
--- a/tools/makedep.c
+++ b/tools/makedep.c
@@ -2685,16 +2685,26 @@ static void output_source_y( struct makefile *make, struct incl_file *source, co

if (find_include_file( make, header ))
     {
+        output( "ifneq (,$(filter grouped-target,$(.FEATURES)))\n" );
+        output( "%s %s.tab.c &: %s\n",
+                obj_dir_path( make, header ), obj_dir_path( make, obj ), source->filename );
+        output( "\t%s%s -o %s.tab.c -d %s\n",
+                cmd_prefix( "BISON" ), bison, obj_dir_path( make, obj ), source->filename );
+        output( "else\n" );
         output( "%s: %s\n", obj_dir_path( make, header ), source->filename );
         output( "\t%s%s -o %s.tab.c -d %s\n",
                 cmd_prefix( "BISON" ), bison, obj_dir_path( make, obj ), source->filename );
         output( "%s.tab.c: %s %s\n", obj_dir_path( make, obj ),
                 source->filename, obj_dir_path( make, header ));
+        output( "\t%s%s -o $@ %s\n", cmd_prefix( "BISON" ), bison, source->filename );
+        output( "endif\n" );
         strarray_add( &make->clean_files, header );
     }
-    else output( "%s.tab.c: %s\n", obj_dir_path( make, obj ), source->filename );
-
-    output( "\t%s%s -o $@ %s\n", cmd_prefix( "BISON" ), bison, source->filename );
+    else
+    {
+        output( "%s.tab.c: %s\n", obj_dir_path( make, obj ), source->filename );
+        output( "\t%s%s -o $@ %s\n", cmd_prefix( "BISON" ), bison, source->filename );
+    }
 }

[Alexandre Julliard (＠julliard)]

Please let's not introduce GNU Make-specific syntax.

[Akihiro Sagawa (＠sgwaki)]

On Wed Sep 13 11:32:55 2023 +0000, Alexandre Julliard wrote:
> Please let's not introduce GNU Make-specific syntax.

All right. I give up this way.

[PATCH 0/1] MR3797: makedep: Make *.tab.c build stable in parallel makes. - closed

[Akihiro Sagawa (＠sgwaki)]

This merge request was closed by Akihiro Sagawa.