Re: [Patch] Don't call linker when creating pre-compiled header just because you saw a linker option

[Steve Ellcey <sellcey at cavium dot com>]

On Tue, 2017-11-14 at 20:04 +0100, Richard Biener wrote:
> 
> I think the intent is to link even for just - lfoo while it makes
> sense to ignore -L/path - Wl,... Certainly counts as possible input. 
> 
> It seems you even break - lfoo. 
> 
> Richard. 

Good point.  I guess I need to take a different approach to determining
if I am creating a PCH or an executable.  Here is a new patch that also
passes the testsuite with no regressions.  Originally in this patch I
was setting create_pch_flag whenever I saw a '@-cheader' compiler being
called but that broke on things like 'gcc foo.h main.c' so now I only
skip the link phase when creating pch's is the only thing being done.

Steve Ellcey
sellcey@cavium.com



2017-11-14  Steve Ellcey  <sellcey@cavium.com>

	* gcc.c (create_pch_flag): New variable.
	(driver::prepare_infiles): Set create_pch_flag
	when we are only creating precompiled headers.
	(driver::maybe_run_linker): Do not link if
	create_pch_flag is set.
	(driver::finalize): Reset create_pch_flag.


diff --git a/gcc/gcc.c b/gcc/gcc.c
index 43e6d59..9df32e3 100644
--- a/gcc/gcc.c
+++ b/gcc/gcc.c
@@ -208,6 +208,9 @@ int is_cpp_driver;
 /* Flag set to nonzero if an @file argument has been supplied to gcc.  */
 static bool at_file_supplied;
 
+/* Flag set to nonzero if we are generating a precompiled header.  */
+static bool create_pch_flag;
+
 /* Definition of string containing the arguments given to configure.  */
 #include "configargs.h"
 
@@ -8074,6 +8077,8 @@ driver::prepare_infiles ()
 {
   size_t i;
   int lang_n_infiles = 0;
+  bool found_pch_input_file = false;
+  bool found_non_pch_input_file = false;
 
   if (n_infiles == added_libraries)
     fatal_error (input_location, "no input files");
@@ -8102,8 +8107,16 @@ driver::prepare_infiles ()
 						   strlen (name),
 						   infiles[i].language);
 
-      if (compiler && !(compiler->combinable))
-	combine_inputs = false;
+      if (compiler)
+	{
+	  if (!(compiler->combinable))
+	    combine_inputs = false;
+
+	  if (strcmp(compiler->suffix, "@c-header") == 0)
+	    found_pch_input_file = true;
+	  else
+	    found_non_pch_input_file = true;
+	}
 
       if (lang_n_infiles > 0 && compiler != input_file_compiler
 	  && infiles[i].language && infiles[i].language[0] != '*')
@@ -8129,6 +8142,9 @@ driver::prepare_infiles ()
     fatal_error (input_location,
 		 "cannot specify -o with -c, -S or -E with multiple files");
 
+  if (found_pch_input_file && !found_non_pch_input_file)
+    create_pch_flag = true;
+
   /* No early exit needed from main; we can continue.  */
   return false;
 }
@@ -8289,6 +8305,10 @@ driver::maybe_run_linker (const char *argv0) const
   int linker_was_run = 0;
   int num_linker_inputs;
 
+  /* If we are creating a precompiled header, do not run the linker.  */
+  if (create_pch_flag)
+    return;
+
   /* Determine if there are any linker input files.  */
   num_linker_inputs = 0;
   for (i = 0; (int) i < n_infiles; i++)
@@ -10059,6 +10079,7 @@ driver::finalize ()
 
   is_cpp_driver = 0;
   at_file_supplied = 0;
+  create_pch_flag = 0;
   print_help_list = 0;
   print_version = 0;
   verbose_only_flag = 0;