ld: Improve --fatal-warnings for unknown command-line options

There are 2 problems with --fatal-warnings for unknown command-line
options:

1. --fatal-warnings doesn't trigger an error for an unknown command-line
option when --fatal-warnings is the last command-line option.
2. When --fatal-warnings triggers an error for an unknown command-line
option, the message says that the unknown command-line option is ignored.

This patch queues unknown command-line option warnings and outputs queued
command-line option warnings after all command-line options have been
processed so that --fatal-warnings can work for unknown command-line
options regardless of the order of --fatal-warnings.

When --fatal-warnings is used, the linker message is changed from

ld: warning: -z bad-option ignored

to

ld: error: unsupported option: -z bad-option

The above also applies to "-z dynamic-undefined-weak" when the known
"-z dynamic-undefined-weak" option is ignored.

	PR ld/31289
	* ldelf.c (ldelf_after_parse): Use queue_unknown_cmdline_warning
	to warn the ignored -z dynamic-undefined-weak option.
	* ldmain.c (main): Call output_unknown_cmdline_warnings after
	calling ldemul_after_parse.
	* ldmisc.c (CMDLINE_WARNING_SIZE): New.
	(cmdline_warning_list): Likewise.
	(cmdline_warning_head): Likewise.
	(cmdline_warning_tail): Likewise.
	(queue_unknown_cmdline_warning): Likewise.
	(output_unknown_cmdline_warnings): Likewise.
	* ldmisc.h (queue_unknown_cmdline_warning): Likewise.
	(output_unknown_cmdline_warnings): Likewise.
	* emultempl/elf.em (gld${EMULATION_NAME}_handle_option): Use
	queue_unknown_cmdline_warning to warn unknown -z option.
	* testsuite/ld-elf/fatal-warnings-1a.d: New file.
	* testsuite/ld-elf/fatal-warnings-1b.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-2a.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-2b.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-3a.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-3b.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-4a.d: Likewise.
	* testsuite/ld-elf/fatal-warnings-4b.d: Likewise.

1 files changed, 75 insertions, 0 deletions

diff --git a/ld/ldmisc.c b/ld/ldmisc.c
index 3c862ea..180b24b 100644
--- a/ld/ldmisc.c
+++ b/ld/ldmisc.c
@@ -620,6 +620,81 @@ einfo (const char *fmt, ...)
   fflush (stderr);
 }
 
+/* The buffer size for each command-line option warning.  */
+#define CMDLINE_WARNING_SIZE	256
+
+/* A linked list of command-line option warnings.  */
+
+struct cmdline_warning_list
+{
+  struct cmdline_warning_list *next;
+  char *warning;
+};
+
+/* The head of the linked list of command-line option warnings.  */
+static struct cmdline_warning_list *cmdline_warning_head = NULL;
+
+/* The tail of the linked list of command-line option warnings.  */
+static struct cmdline_warning_list **cmdline_warning_tail
+  = &cmdline_warning_head;
+
+/* Queue an unknown command-line option warning.  */
+
+void
+queue_unknown_cmdline_warning (const char *fmt, ...)
+{
+  va_list arg;
+  struct cmdline_warning_list *warning_ptr
+    = xmalloc (sizeof (*warning_ptr));
+  warning_ptr->warning = xmalloc (CMDLINE_WARNING_SIZE);
+  warning_ptr->next = NULL;
+  int written;
+
+  va_start (arg, fmt);
+  written = vsnprintf (warning_ptr->warning, CMDLINE_WARNING_SIZE, fmt,
+		       arg);
+  if (written < 0 || written >= CMDLINE_WARNING_SIZE)
+    {
+      /* If vsnprintf fails or truncates, output the warning directly.  */
+      fflush (stdout);
+      va_start (arg, fmt);
+      vfinfo (stderr, fmt, arg, true);
+      fflush (stderr);
+    }
+  else
+    {
+      *cmdline_warning_tail = warning_ptr;
+      cmdline_warning_tail = &warning_ptr->next;
+    }
+  va_end (arg);
+}
+
+/* Output queued unknown command-line option warnings.  */
+
+void
+output_unknown_cmdline_warnings (void)
+{
+  struct cmdline_warning_list *list = cmdline_warning_head;
+  struct cmdline_warning_list *next;
+  if (list == NULL)
+    return;
+
+  fflush (stdout);
+
+  for (; list != NULL; list = next)
+    {
+      next = list->next;
+      if (config.fatal_warnings)
+	einfo (_("%P: error: unsupported option: %s\n"), list->warning);
+      else
+	einfo (_("%P: warning: %s ignored\n"), list->warning);
+      free (list->warning);
+      free (list);
+    }
+
+  fflush (stderr);
+}
+
 void
 info_assert (const char *file, unsigned int line)
 {