[gcc r15-5705] selftest: invoke "diff" when ASSERT_STREQ fails

[David Malcolm via Gcc-cvs]

https://gcc.gnu.org/g:746629e22888b376f95c45779db40bfbfe2ab282

commit r15-5705-g746629e22888b376f95c45779db40bfbfe2ab282
Author: David Malcolm <dmalc...@redhat.com>
Date:   Tue Nov 26 16:09:37 2024 -0500

    selftest: invoke "diff" when ASSERT_STREQ fails
    
    Currently when ASSERT_STREQ or ASSERT_STREQ_AT fail we print
    both strings to stderr.  However it can be hard to figure out
    the problem (e.g. for 1-character differences in long strings).
    
    Extend the output by writing out the strings to tempfiles and
    invoking "diff -up" on them when we have such a selftest failure,
    to (I hope) simplify debugging.
    
    gcc/ChangeLog:
            * selftest.cc (selftest::print_diff): New function.
            (selftest::assert_streq): Call it when we have non-equal
            non-null strings.
    
    Signed-off-by: David Malcolm <dmalc...@redhat.com>

Diff:
---
 gcc/selftest.cc | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/gcc/selftest.cc b/gcc/selftest.cc
index 15284c3359c4..7ab7889cf8c5 100644
--- a/gcc/selftest.cc
+++ b/gcc/selftest.cc
@@ -63,6 +63,26 @@ fail_formatted (const location &loc, const char *fmt, ...)
   abort ();
 }
 
+/* Invoke "diff" to print the difference between VAL1 and VAL2
+   on stdout.  */
+
+static void
+print_diff (const location &loc, const char *val1, const char *val2)
+{
+  temp_source_file tmpfile1 (loc, ".txt", val1);
+  temp_source_file tmpfile2 (loc, ".txt", val2);
+  const char *args[] = {"diff",
+                       "-up",
+                       tmpfile1.get_filename (),
+                       tmpfile2.get_filename (),
+                       NULL};
+  int exit_status = 0;
+  int err = 0;
+  pex_one (PEX_SEARCH | PEX_LAST,
+          args[0], CONST_CAST (char **, args),
+          NULL, NULL, NULL, &exit_status, &err);
+}
+
 /* Implementation detail of ASSERT_STREQ.
    Compare val1 and val2 with strcmp.  They ought
    to be non-NULL; fail gracefully if either or both are NULL.  */
@@ -89,8 +109,12 @@ assert_streq (const location &loc,
        if (strcmp (val1, val2) == 0)
          pass (loc, "ASSERT_STREQ");
        else
-         fail_formatted (loc, "ASSERT_STREQ (%s, %s)\n val1=\"%s\"\n 
val2=\"%s\"\n",
-                         desc_val1, desc_val2, val1, val2);
+         {
+           print_diff (loc, val1, val2);
+           fail_formatted
+             (loc, "ASSERT_STREQ (%s, %s)\n val1=\"%s\"\n val2=\"%s\"\n",
+              desc_val1, desc_val2, val1, val2);
+         }
       }
 }