bug#49623: Guile 3.0.7 can't read #{{}}#

bug#49623: Guile 3.0.7 can't read #{{}}#

[Maxime Devos]

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Hi,

A scheme library I'm working on now fails to compile
after switching from 3.0.2 to Guile 3.0.7.  The issue
is that Guile can't read #{{}}# anymore.

In guile 3.0.7:

scheme@(guile-user)> '#{{}}# }#
$1 = #{\x7b;\x7d;# }# ; the }# should result in a syntax error
scheme@(guile-user)> '#{{}}# ; this should work
...
; ^ guile is waiting for input

In guile 3.0.2:
scheme@(guile-user)> '#{{}}#
$1 = #{\x7b;\x7d;}# ; ok!

(Yes, I really name my variables like that sometimes.)

Note that #{{}a}# can be read just fine by both guile versions.

Greetings,
Maxime.

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bug#49623: [PATCH] Parse #{{}}# properly.

[Maxime Devos]

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Hi guilers,

This fixes bug #49623.  I also added two additional test cases.
I'm rebuilding Guile right now and will re-run the entire test suite,
and I'll build the affected guile library with the fixed guile.

Greetings,
Maxime.

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From 9fb7cff1a2544aae3827db1a781be6e5c367d8c0 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Sun, 18 Jul 2021 19:59:32 +0200
Subject: [PATCH] ice-9/read: Parse #{}}# properly.

This is a regression since Guile 3.0.2 and breaks compilation
of a Guile library.

* module/ice-9/read.scm
  (%read)[read-parenthesized]: When 'saw-brace?' is #t, do not
  reset 'saw-brace?' to #f if the current character is #\}.
* test-suite/tests/reader.test
  ("#{}#): Add two test cases.
---
 module/ice-9/read.scm        | 5 ++++-
 test-suite/tests/reader.test | 3 +++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/module/ice-9/read.scm b/module/ice-9/read.scm
index 72811fdb8..3fcc6ae50 100644
--- a/module/ice-9/read.scm
+++ b/module/ice-9/read.scm
@@ -570,7 +570,10 @@
            (saw-brace?
             (if (eqv? ch #\#)
                 '()
-                (cons #\} (lp #f))))
+                ;; (eqv? ch #\}) is required instead of #f to allow for
+                ;; the trailing # to be preceded by two }, e.g.
+                ;; #{}}# or #{{a}}#.  See <https://bug.gnu.org/XXX>.
+                (cons #\} (lp (eqv? ch #\})))))
            ((eqv? ch #\})
             (lp #t))
            ((eqv? ch #\\)
diff --git a/test-suite/tests/reader.test b/test-suite/tests/reader.test
index ef11a4abd..134cb5ec3 100644
--- a/test-suite/tests/reader.test
+++ b/test-suite/tests/reader.test
@@ -508,6 +508,9 @@
 
 (with-test-prefix "#{}#"
   (pass-if (equal? (read-string "#{}#") '#{}#))
+  ;; ??? bugs.gnu.org
+  (pass-if (equal? (read-string "#{{}}#") (string->symbol "{}")))
+  (pass-if (equal? (read-string "#{{}b}#") (string->symbol "{}b")))
   (pass-if (not (equal? (read-string "(a #{.}# b)") '(a . b))))
   (pass-if (equal? (read-string "#{a}#") 'a))
   (pass-if (equal? (read-string "#{a b}#") '#{a b}#))
-- 
2.32.0


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bug#49623: Fwd: [PATCH] Parse #{{}}# properly.

[Maxime Devos]

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It turns out that the test fails when the patch
is applies to guile@3.0.7.  I'll rebase and try
to figure things out.

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bug#49623: [PATCH v2] Parse #{{}}# properly.

[Maxime Devos]

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Maxime Devos schreef op zo 18-07-2021 om 21:47 [+0200]:
> It turns out that the test fails when the patch
> is applies to guile@3.0.7.  I'll rebase and try
> to figure things out.

With the revised patch, tests succeed and the Guile
library now compiles successfully.

Greetings,
Maxime.

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From 40b0b29c05d521cd8901988fa2bc71547f917f48 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Sun, 18 Jul 2021 19:59:32 +0200
Subject: [PATCH] ice-9/read: Parse #{}}# properly.

This is a regression since Guile 3.0.2 and breaks compilation
of a Guile library.

* module/ice-9/read.scm
  (%read)[read-parenthesized]: When SAW-BRACE? is #t but CH isn't
  #\#, don't eat CH.
* test-suite/tests/reader.test
  ("#{}#): Add four test cases.
---
 module/ice-9/read.scm        | 7 +++++--
 test-suite/tests/reader.test | 5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/module/ice-9/read.scm b/module/ice-9/read.scm
index ac407739f..283933064 100644
--- a/module/ice-9/read.scm
+++ b/module/ice-9/read.scm
@@ -556,12 +556,15 @@
     (string->symbol
      (list->string
       (let lp ((saw-brace? #f))
-        (let ((ch (next-not-eof)))
+        (let lp/inner ((ch (next-not-eof))
+                       (saw-brace? saw-brace?))
           (cond
            (saw-brace?
             (if (eqv? ch #\#)
                 '()
-                (cons #\} (lp #f))))
+                ;; Don't eat CH, see
+                ;; <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49623>.
+                (cons #\} (lp/inner ch #f))))
            ((eqv? ch #\})
             (lp #t))
            ((eqv? ch #\\)
diff --git a/test-suite/tests/reader.test b/test-suite/tests/reader.test
index 1481a0a5d..ad7c6d575 100644
--- a/test-suite/tests/reader.test
+++ b/test-suite/tests/reader.test
@@ -536,6 +536,11 @@
 
 (with-test-prefix "#{}#"
   (pass-if (equal? (read-string "#{}#") '#{}#))
+  ;; See <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49623>
+  (pass-if (equal? (read-string "#{}}#") (string->symbol "}")))
+  (pass-if (equal? (read-string "#{}}}#") (string->symbol "}}")))
+  (pass-if (equal? (read-string "#{{}}#") (string->symbol "{}")))
+  (pass-if (equal? (read-string "#{{}b}#") (string->symbol "{}b")))
   (pass-if (not (equal? (read-string "(a #{.}# b)") '(a . b))))
   (pass-if (equal? (read-string "#{a}#") 'a))
   (pass-if (equal? (read-string "#{a b}#") '#{a b}#))
-- 
2.32.0


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bug#49623: [PATCH v2] Parse #{{}}# properly.

[lloda]

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Applied in c78c130b1ddef6d6c290533f74ce1fbd51a4b19d. Thank you!


> On 20 Jul 2021, at 12:54, Maxime Devos <maximedevos@telenet.be> wrote:
> 
> Maxime Devos schreef op zo 18-07-2021 om 21:47 [+0200]:
>> It turns out that the test fails when the patch
>> is applies to guile@3.0.7.  I'll rebase and try
>> to figure things out.
> 
> With the revised patch, tests succeed and the Guile
> library now compiles successfully.
> 
> Greetings,
> Maxime.

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From 40b0b29c05d521cd8901988fa2bc71547f917f48 Mon Sep 17 00:00:00 2001
From: Maxime Devos <maximedevos@telenet.be>
Date: Sun, 18 Jul 2021 19:59:32 +0200
Subject: [PATCH] ice-9/read: Parse #{}}# properly.

This is a regression since Guile 3.0.2 and breaks compilation
of a Guile library.

* module/ice-9/read.scm
  (%read)[read-parenthesized]: When SAW-BRACE? is #t but CH isn't
  #\#, don't eat CH.
* test-suite/tests/reader.test
  ("#{}#): Add four test cases.
---
 module/ice-9/read.scm        | 7 +++++--
 test-suite/tests/reader.test | 5 +++++
 2 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/module/ice-9/read.scm b/module/ice-9/read.scm
index ac407739f..283933064 100644
--- a/module/ice-9/read.scm
+++ b/module/ice-9/read.scm
@@ -556,12 +556,15 @@
     (string->symbol
      (list->string
       (let lp ((saw-brace? #f))
-        (let ((ch (next-not-eof)))
+        (let lp/inner ((ch (next-not-eof))
+                       (saw-brace? saw-brace?))
           (cond
            (saw-brace?
             (if (eqv? ch #\#)
                 '()
-                (cons #\} (lp #f))))
+                ;; Don't eat CH, see
+                ;; <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49623>.
+                (cons #\} (lp/inner ch #f))))
            ((eqv? ch #\})
             (lp #t))
            ((eqv? ch #\\)
diff --git a/test-suite/tests/reader.test b/test-suite/tests/reader.test
index 1481a0a5d..ad7c6d575 100644
--- a/test-suite/tests/reader.test
+++ b/test-suite/tests/reader.test
@@ -536,6 +536,11 @@
 
 (with-test-prefix "#{}#"
   (pass-if (equal? (read-string "#{}#") '#{}#))
+  ;; See <https://debbugs.gnu.org/cgi/bugreport.cgi?bug=49623>
+  (pass-if (equal? (read-string "#{}}#") (string->symbol "}")))
+  (pass-if (equal? (read-string "#{}}}#") (string->symbol "}}")))
+  (pass-if (equal? (read-string "#{{}}#") (string->symbol "{}")))
+  (pass-if (equal? (read-string "#{{}b}#") (string->symbol "{}b")))
   (pass-if (not (equal? (read-string "(a #{.}# b)") '(a . b))))
   (pass-if (equal? (read-string "#{a}#") 'a))
   (pass-if (equal? (read-string "#{a b}#") '#{a b}#))
-- 
2.32.0


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