[PATCH 2/2] Add --save-temps/-s

[PATCH 2/2] Add --save-temps/-s

[Tom de Vries]

Hi,

The temporary files used in multifile mode are of interest when debugging
multifile issues, but they are removed after dwz has run.

Add a developer-only (that is, not added to usage or manual) option
--save-temps/-s to keep these files available:
...
$ dwz --save-temps -m 3 1 2
$ ls -1 dwz.*
dwz.debug_abbrev.IklrhP
dwz.debug_info.CWGFOC
dwz.debug_line.Dx6cK1
dwz.debug_macro.Yjq9Fq
dwz.debug_str.uZ1Yce
...

These files can then be added to a dummy elf file, which can be inspected
using readelf or some such:
...
$ echo 'int a;' | gcc -xc - -c -o mf.o
$ for f in dwz.debug_*; do
      section=$(echo $f \
                    | sed 's/^dwz\.//;s/\..*//')
      objcopy \
          --add-section .$section=$f \
          mf.o
  done
$ readelf -w mf.o > READELF
...

OK for trunk?

Thanks,
- Tom

Add --save-temps/-s

2019-02-15  Tom de Vries  <tdevries@suse.de>

	* dwz.c (save_temps): New variable.
	(dwz_options): Add -save-temps entry.
	(TMPDIR): Define.
	(make_temp_file): Handle save_temps.
	(main): Set save_temps.

---
 dwz.c | 45 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 32 insertions(+), 13 deletions(-)

diff --git a/dwz.c b/dwz.c
index c8ada61..426bebc 100644
--- a/dwz.c
+++ b/dwz.c
@@ -485,6 +485,8 @@ static int multi_info_fd = -1, multi_abbrev_fd = -1;
 static int multi_line_fd = -1, multi_str_fd = -1;
 static int multi_macro_fd = -1;
 
+bool save_temps = false;
+
 /* Copy of one of the input file's ehdr.  */
 static GElf_Ehdr multi_ehdr;
 
@@ -11762,6 +11764,7 @@ static struct option dwz_options[] =
   { "multifile",	 required_argument, 0, 'm' },
   { "quiet",		 no_argument,	    0, 'q' },
   { "hardlink",		 no_argument,	    0, 'h' },
+  { "save-temps",	 no_argument,	    0, 's' },
   { "low-mem-die-limit", required_argument, 0, 'l' },
   { "max-die-limit",	 required_argument, 0, 'L' },
   { "multifile-name",	 required_argument, 0, 'M' },
@@ -11794,26 +11797,37 @@ version (void)
   exit (0);
 }
 
+#define TMPDIR "/tmp/"
+
 /* Create a temporary file using TEMPLATE.  Return the corresponding file
    descriptor if successful, otherwise return -1.  */
 static int
 make_temp_file (const char *template)
 {
-  char buf[sizeof "/tmp/dwz.debug_abbrev.XXXXXX"];
+  char buf[sizeof TMPDIR "dwz.debug_abbrev.XXXXXX"];
+  char *s = buf;
   int fd;
-  size_t template_len;
+  size_t template_len, tmpdir_len;
 
+  tmpdir_len = strlen (TMPDIR);
   template_len = strlen (template);
-  assert (template_len + 1 <= sizeof buf);
-  strncpy (buf, template, sizeof buf);
+  assert (tmpdir_len + template_len + 1 <= sizeof buf);
+
+  if (!save_temps)
+    {
+      strncpy (s, TMPDIR, sizeof buf);
+      s += tmpdir_len;
+    }
+  strncpy (s, template, sizeof buf - tmpdir_len);
 
   fd = mkstemp (buf);
   if (fd == -1)
     return fd;
 
-  /* Unlink the filename, such that the file is disposed of once the file
-     descriptor is closed.  */
-  unlink (buf);
+  if (!save_temps)
+    /* Unlink the filename, such that the file is disposed of once the file
+       descriptor is closed.  */
+    unlink (buf);
 
   return fd;
 }
@@ -11835,7 +11849,8 @@ main (int argc, char *argv[])
   while (1)
     {
       int option_index;
-      int c = getopt_long (argc, argv, "m:o:qhl:L:M:r?v", dwz_options, &option_index);
+      int c = getopt_long (argc, argv, "m:o:qhl:L:M:r?vs", dwz_options,
+			   &option_index);
       if (c == -1)
 	break;
       switch (c)
@@ -11861,6 +11876,10 @@ main (int argc, char *argv[])
 	  hardlink = true;
 	  break;
 
+	case 's':
+	  save_temps = true;
+	  break;
+
 	case 'M':
 	  multifile_name = optarg;
 	  break;
@@ -11921,11 +11940,11 @@ main (int argc, char *argv[])
 	error (1, 0, "-o option not allowed for multiple files");
       if (multifile)
 	{
-	  multi_info_fd = make_temp_file ("/tmp/dwz.debug_info.XXXXXX");
-	  multi_abbrev_fd = make_temp_file ("/tmp/dwz.debug_abbrev.XXXXXX");
-	  multi_line_fd = make_temp_file ("/tmp/dwz.debug_line.XXXXXX");
-	  multi_str_fd = make_temp_file ("/tmp/dwz.debug_str.XXXXXX");
-	  multi_macro_fd = make_temp_file ("/tmp/dwz.debug_macro.XXXXXX");
+	  multi_info_fd = make_temp_file ("dwz.debug_info.XXXXXX");
+	  multi_abbrev_fd = make_temp_file ("dwz.debug_abbrev.XXXXXX");
+	  multi_line_fd = make_temp_file ("dwz.debug_line.XXXXXX");
+	  multi_str_fd = make_temp_file ("dwz.debug_str.XXXXXX");
+	  multi_macro_fd = make_temp_file ("dwz.debug_macro.XXXXXX");
 	  if (multi_info_fd == -1
 	      || multi_abbrev_fd == -1
 	      || multi_line_fd == -1