From 101996d9ac64ef1d66a630223cd82451dc930900 Mon Sep 17 00:00:00 2001
From: Wondr <wondr.design@gmail.com>
Date: Thu, 4 Jun 2026 23:13:39 +0100
Subject: [PATCH] grep: honor GNU buffer anchors in BRE

---
 src/matcher.rs     |  4 ++++
 tests/test_grep.rs | 12 ++++++++++++
 2 files changed, 16 insertions(+)

diff --git a/src/matcher.rs b/src/matcher.rs
index d9cf846..c1be567 100644
--- a/src/matcher.rs
+++ b/src/matcher.rs
@@ -215,6 +215,10 @@ impl CompiledPattern {
             // GNU grep supports `{,n}` as an alias for `{0,n}`.
             syntax.enable_behavior(SyntaxBehavior::SYNTAX_BEHAVIOR_ALLOW_INTERVAL_LOW_ABBREV);
         }
+        if config.regex_mode == RegexMode::Basic {
+            // GNU grep treats \` and \' as buffer anchors.
+            syntax.enable_operators(SyntaxOperator::SYNTAX_OPERATOR_ESC_GNU_BUF_ANCHOR);
+        }
         if config.regex_mode == RegexMode::Perl {
             // GNU grep supports `(?P<name>...)`.
             // Unfortunately, the onig crate defines the OP2 flag without the
diff --git a/tests/test_grep.rs b/tests/test_grep.rs
index d061918..79dc9a8 100644
--- a/tests/test_grep.rs
+++ b/tests/test_grep.rs
@@ -70,6 +70,18 @@ fn bre_gnu_extensions() {
         .succeeds()
         .stdout_only("contain\n");
 
+    let (_s, mut c) = ucmd();
+    c.args(&[r"\`c"])
+        .pipe_in("cat\nscat\n")
+        .succeeds()
+        .stdout_only("cat\n");
+
+    let (_s, mut c) = ucmd();
+    c.args(&[r"t\'"])
+        .pipe_in("cat\ntab\n")
+        .succeeds()
+        .stdout_only("cat\n");
+
     // BRE backreference: repeated adjacent word.
     let (_s, mut c) = ucmd();
     c.args(&[r"\(\b\w\+\b\) \1"])