[gcc(refs/users/marxin/heads/PR104333-lto-error-handling)] lto: fix error handling for -Wl, -plugin-opt=debug

[Martin Liska <marxin@gcc.gnu.org>]

https://gcc.gnu.org/g:818e357c9a0fd984bfe48e1fedb36e6e9577cd85

commit 818e357c9a0fd984bfe48e1fedb36e6e9577cd85
Author: Martin Liska <mliska@suse.cz>
Date:   Wed Feb 2 14:21:51 2022 +0100

    lto: fix error handling for -Wl,-plugin-opt=debug
    
    When one uses something like: -Wl,-plugin-opt=debug,
    we end up with lto1 WPA invocation that has 'debug'
    on command line. We interpret that as input filename.
    
    The patch moves resolution checking later so that we end up with
    a reasonable error message:
    
    lto1: error: open debug failed: No such file or directory
    lto1: fatal error: errors during merging of translation units
    
            PR lto/104333
    
    gcc/lto/ChangeLog:
    
            * lto-common.cc (read_cgraph_and_symbols): Move resolution
            checking for number of files later and report a reasonable
            error message.

Diff:
---
 gcc/lto/lto-common.cc | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/gcc/lto/lto-common.cc b/gcc/lto/lto-common.cc
index 4d6686b0b99..fbcd4742ee4 100644
--- a/gcc/lto/lto-common.cc
+++ b/gcc/lto/lto-common.cc
@@ -2704,6 +2704,7 @@ read_cgraph_and_symbols (unsigned nfiles, const char **fnames)
 {
   unsigned int i, last_file_ix;
   FILE *resolution;
+  unsigned resolution_objects = 0;
   int count = 0;
   struct lto_file_decl_data **decl_data;
   symtab_node *snode;
@@ -2726,18 +2727,14 @@ read_cgraph_and_symbols (unsigned nfiles, const char **fnames)
   if (resolution_file_name)
     {
       int t;
-      unsigned num_objects;
 
       resolution = fopen (resolution_file_name, "r");
       if (resolution == NULL)
 	fatal_error (input_location,
 		     "could not open symbol resolution file: %m");
 
-      t = fscanf (resolution, "%u", &num_objects);
+      t = fscanf (resolution, "%u", &resolution_objects);
       gcc_assert (t == 1);
-
-      /* True, since the plugin splits the archives.  */
-      gcc_assert (num_objects == nfiles);
     }
   symtab->state = LTO_STREAMING;
 
@@ -2806,7 +2803,12 @@ read_cgraph_and_symbols (unsigned nfiles, const char **fnames)
   lto_register_canonical_types_for_odr_types ();
 
   if (resolution_file_name)
-    fclose (resolution);
+    {
+      /* True, since the plugin splits the archives.  */
+      if (!seen_error ())
+	gcc_assert (resolution_objects == nfiles);
+      fclose (resolution);
+    }
 
   /* Show the LTO report before launching LTRANS.  */
   if (flag_lto_report || (flag_wpa && flag_lto_report_wpa))