[PATCH 0/2] Fix a crash in go-lang.c

[PATCH 0/2] Fix a crash in go-lang.c

[Tom Tromey]

This series fixes a crash in go-lang.c, but first it takes a detour to
remove some manual memory management.

---
Tom Tromey (2):
      Avoid manual memory management in go-lang.c
      Fix crash in go_symbol_package_name

 gdb/dwarf2/read.c                   |  2 +-
 gdb/go-exp.y                        |  8 +++----
 gdb/go-lang.c                       | 43 +++++++++++++++++--------------------
 gdb/go-lang.h                       | 11 +++++++---
 gdb/testsuite/gdb.go/no-package.exp | 31 ++++++++++++++++++++++++++
 5 files changed, 64 insertions(+), 31 deletions(-)
---
base-commit: 16b84b6599dba01abc00954d0bc80ddf0c2373e3
change-id: 20230216-submit-go-unique-ptr-5aefe0b36452

Best regards,
-- 
Tom Tromey <tom@tromey.com>

[PATCH 1/2] Avoid manual memory management in go-lang.c

[Tom Tromey]

I noticed a couple of spots in go-lang.c that could be improved by
using unique_ptr.
---
 gdb/dwarf2/read.c |  2 +-
 gdb/go-exp.y      |  8 ++++----
 gdb/go-lang.c     | 40 ++++++++++++++++++----------------------
 gdb/go-lang.h     | 11 ++++++++---
 4 files changed, 31 insertions(+), 30 deletions(-)

diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
index eb37c776989..4fd46fd43f8 100644
--- a/gdb/dwarf2/read.c
+++ b/gdb/dwarf2/read.c
@@ -5838,7 +5838,7 @@ fixup_go_packaging (struct dwarf2_cu *cu)
 	      && sym->aclass () == LOC_BLOCK)
 	    {
 	      gdb::unique_xmalloc_ptr<char> this_package_name
-		(go_symbol_package_name (sym));
+		= go_symbol_package_name (sym);
 
 	      if (this_package_name == NULL)
 		continue;
diff --git a/gdb/go-exp.y b/gdb/go-exp.y
index 242e7103b94..6aa4c426df6 100644
--- a/gdb/go-exp.y
+++ b/gdb/go-exp.y
@@ -1396,16 +1396,16 @@ classify_name (struct parser_state *par_state, const struct block *block)
      current package.  */
 
   {
-    char *current_package_name = go_block_package_name (block);
+    gdb::unique_xmalloc_ptr<char> current_package_name
+      = go_block_package_name (block);
 
     if (current_package_name != NULL)
       {
 	struct stoken sval =
-	  build_packaged_name (current_package_name,
-			       strlen (current_package_name),
+	  build_packaged_name (current_package_name.get (),
+			       strlen (current_package_name.get ()),
 			       copy.c_str (), copy.size ());
 
-	xfree (current_package_name);
 	sym = lookup_symbol (sval.ptr, block, VAR_DOMAIN,
 			     &is_a_field_of_this);
 	if (sym.symbol)
diff --git a/gdb/go-lang.c b/gdb/go-lang.c
index 7549f14dc63..f9176ace71d 100644
--- a/gdb/go-lang.c
+++ b/gdb/go-lang.c
@@ -163,11 +163,8 @@ unpack_package_and_object (char *buf,
 
    Space for the resulting strings is malloc'd in one buffer.
    PACKAGEP,OBJECTP,METHOD_TYPE* will (typically) point into this buffer.
-   [There are a few exceptions, but the caller is still responsible for
-   freeing the resulting pointer.]
    A pointer to this buffer is returned, or NULL if symbol isn't a
    mangled Go symbol.
-   The caller is responsible for freeing the result.
 
    *METHOD_TYPE_IS_POINTERP is set to a boolean indicating if
    the method type is a pointer.
@@ -180,7 +177,7 @@ unpack_package_and_object (char *buf,
    If we ever need to unpack the method type, this routine should work
    for that too.  */
 
-static char *
+static gdb::unique_xmalloc_ptr<char>
 unpack_mangled_go_symbol (const char *mangled_name,
 			  const char **packagep,
 			  const char **objectp,
@@ -209,9 +206,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
   /* main.init is mangled specially.  */
   if (strcmp (mangled_name, "__go_init_main") == 0)
     {
-      char *package = xstrdup ("main");
+      gdb::unique_xmalloc_ptr<char> package
+	= make_unique_xstrdup ("main");
 
-      *packagep = package;
+      *packagep = package.get ();
       *objectp = "init";
       return package;
     }
@@ -219,9 +217,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
   /* main.main is mangled specially (missing prefix).  */
   if (strcmp (mangled_name, "main.main") == 0)
     {
-      char *package = xstrdup ("main");
+      gdb::unique_xmalloc_ptr<char> package
+	= make_unique_xstrdup ("main");
 
-      *packagep = package;
+      *packagep = package.get ();
       *objectp = "main";
       return package;
     }
@@ -261,7 +260,8 @@ unpack_mangled_go_symbol (const char *mangled_name,
 
   /* At this point we've decided we have a mangled Go symbol.  */
 
-  buf = xstrdup (mangled_name);
+  gdb::unique_xmalloc_ptr<char> result = make_unique_xstrdup (mangled_name);
+  buf = result.get ();
 
   /* Search backwards looking for "N<digit(s)>".  */
   p = buf + len;
@@ -317,7 +317,7 @@ unpack_mangled_go_symbol (const char *mangled_name,
     }
 
   unpack_package_and_object (buf, packagep, objectp);
-  return buf;
+  return result;
 }
 
 /* Implements the la_demangle language_defn routine for language Go.
@@ -381,10 +381,9 @@ go_language::demangle_symbol (const char *mangled_name, int options) const
   return make_unique_xstrdup ((const char *) obstack_finish (&tempbuf));
 }
 
-/* Given a Go symbol, return its package or NULL if unknown.
-   Space for the result is malloc'd, caller must free.  */
+/* See go-lang.h.  */
 
-char *
+gdb::unique_xmalloc_ptr<char>
 go_symbol_package_name (const struct symbol *sym)
 {
   const char *mangled_name = sym->linkage_name ();
@@ -393,8 +392,7 @@ go_symbol_package_name (const struct symbol *sym)
   const char *method_type_package_name;
   const char *method_type_object_name;
   int method_type_is_pointer;
-  char *name_buf;
-  char *result;
+  gdb::unique_xmalloc_ptr<char> name_buf;
 
   gdb_assert (sym->language () == language_go);
   name_buf = unpack_mangled_go_symbol (mangled_name,
@@ -405,15 +403,12 @@ go_symbol_package_name (const struct symbol *sym)
   /* Some Go symbols don't have mangled form we interpret (yet).  */
   if (name_buf == NULL)
     return NULL;
-  result = xstrdup (package_name);
-  xfree (name_buf);
-  return result;
+  return make_unique_xstrdup (package_name);
 }
 
-/* Return the package that BLOCK is in, or NULL if there isn't one.
-   Space for the result is malloc'd, caller must free.  */
+/* See go-lang.h.  */
 
-char *
+gdb::unique_xmalloc_ptr<char>
 go_block_package_name (const struct block *block)
 {
   while (block != NULL)
@@ -422,7 +417,8 @@ go_block_package_name (const struct block *block)
 
       if (function != NULL)
 	{
-	  char *package_name = go_symbol_package_name (function);
+	  gdb::unique_xmalloc_ptr<char> package_name
+	    = go_symbol_package_name (function);
 
 	  if (package_name != NULL)
 	    return package_name;
diff --git a/gdb/go-lang.h b/gdb/go-lang.h
index 1820b4c9658..877b6175534 100644
--- a/gdb/go-lang.h
+++ b/gdb/go-lang.h
@@ -63,9 +63,14 @@ extern const char *go_main_name (void);
 
 extern enum go_type go_classify_struct_type (struct type *type);
 
-extern char *go_symbol_package_name (const struct symbol *sym);
-
-extern char *go_block_package_name (const struct block *block);
+/* Given a Go symbol, return its package or NULL if unknown.  */
+extern gdb::unique_xmalloc_ptr<char> go_symbol_package_name
+     (const struct symbol *sym);
+
+/* Return the package that BLOCK is in, or NULL if there isn't
+   one.  */
+extern gdb::unique_xmalloc_ptr<char> go_block_package_name
+     (const struct block *block);
 
 extern const struct builtin_go_type *builtin_go_type (struct gdbarch *);
 

-- 
2.39.1

Re: [PATCH 1/2] Avoid manual memory management in go-lang.c

[Andrew Burgess]

Tom Tromey <tom@tromey.com> writes:

> I noticed a couple of spots in go-lang.c that could be improved by
> using unique_ptr.
> ---
>  gdb/dwarf2/read.c |  2 +-
>  gdb/go-exp.y      |  8 ++++----
>  gdb/go-lang.c     | 40 ++++++++++++++++++----------------------
>  gdb/go-lang.h     | 11 ++++++++---
>  4 files changed, 31 insertions(+), 30 deletions(-)
>
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index eb37c776989..4fd46fd43f8 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -5838,7 +5838,7 @@ fixup_go_packaging (struct dwarf2_cu *cu)
>  	      && sym->aclass () == LOC_BLOCK)
>  	    {
>  	      gdb::unique_xmalloc_ptr<char> this_package_name
> -		(go_symbol_package_name (sym));
> +		= go_symbol_package_name (sym);
>  
>  	      if (this_package_name == NULL)
>  		continue;
> diff --git a/gdb/go-exp.y b/gdb/go-exp.y
> index 242e7103b94..6aa4c426df6 100644
> --- a/gdb/go-exp.y
> +++ b/gdb/go-exp.y
> @@ -1396,16 +1396,16 @@ classify_name (struct parser_state *par_state, const struct block *block)
>       current package.  */
>  
>    {
> -    char *current_package_name = go_block_package_name (block);
> +    gdb::unique_xmalloc_ptr<char> current_package_name
> +      = go_block_package_name (block);
>  
>      if (current_package_name != NULL)
>        {
>  	struct stoken sval =
> -	  build_packaged_name (current_package_name,
> -			       strlen (current_package_name),
> +	  build_packaged_name (current_package_name.get (),
> +			       strlen (current_package_name.get ()),
>  			       copy.c_str (), copy.size ());
>  
> -	xfree (current_package_name);
>  	sym = lookup_symbol (sval.ptr, block, VAR_DOMAIN,
>  			     &is_a_field_of_this);
>  	if (sym.symbol)
> diff --git a/gdb/go-lang.c b/gdb/go-lang.c
> index 7549f14dc63..f9176ace71d 100644
> --- a/gdb/go-lang.c
> +++ b/gdb/go-lang.c
> @@ -163,11 +163,8 @@ unpack_package_and_object (char *buf,
>  
>     Space for the resulting strings is malloc'd in one buffer.
>     PACKAGEP,OBJECTP,METHOD_TYPE* will (typically) point into this buffer.
> -   [There are a few exceptions, but the caller is still responsible for
> -   freeing the resulting pointer.]
>     A pointer to this buffer is returned, or NULL if symbol isn't a
>     mangled Go symbol.
> -   The caller is responsible for freeing the result.
>  
>     *METHOD_TYPE_IS_POINTERP is set to a boolean indicating if
>     the method type is a pointer.
> @@ -180,7 +177,7 @@ unpack_package_and_object (char *buf,
>     If we ever need to unpack the method type, this routine should work
>     for that too.  */
>  
> -static char *
> +static gdb::unique_xmalloc_ptr<char>
>  unpack_mangled_go_symbol (const char *mangled_name,
>  			  const char **packagep,
>  			  const char **objectp,
> @@ -209,9 +206,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
>    /* main.init is mangled specially.  */
>    if (strcmp (mangled_name, "__go_init_main") == 0)
>      {
> -      char *package = xstrdup ("main");
> +      gdb::unique_xmalloc_ptr<char> package
> +	= make_unique_xstrdup ("main");
>  
> -      *packagep = package;
> +      *packagep = package.get ();
>        *objectp = "init";
>        return package;
>      }
> @@ -219,9 +217,10 @@ unpack_mangled_go_symbol (const char *mangled_name,
>    /* main.main is mangled specially (missing prefix).  */
>    if (strcmp (mangled_name, "main.main") == 0)
>      {
> -      char *package = xstrdup ("main");
> +      gdb::unique_xmalloc_ptr<char> package
> +	= make_unique_xstrdup ("main");
>  
> -      *packagep = package;
> +      *packagep = package.get ();
>        *objectp = "main";
>        return package;
>      }
> @@ -261,7 +260,8 @@ unpack_mangled_go_symbol (const char *mangled_name,
>  
>    /* At this point we've decided we have a mangled Go symbol.  */
>  
> -  buf = xstrdup (mangled_name);
> +  gdb::unique_xmalloc_ptr<char> result = make_unique_xstrdup (mangled_name);
> +  buf = result.get ();
>  
>    /* Search backwards looking for "N<digit(s)>".  */
>    p = buf + len;
> @@ -317,7 +317,7 @@ unpack_mangled_go_symbol (const char *mangled_name,
>      }
>  
>    unpack_package_and_object (buf, packagep, objectp);
> -  return buf;
> +  return result;
>  }
>  
>  /* Implements the la_demangle language_defn routine for language Go.
> @@ -381,10 +381,9 @@ go_language::demangle_symbol (const char *mangled_name, int options) const
>    return make_unique_xstrdup ((const char *) obstack_finish (&tempbuf));
>  }
>  
> -/* Given a Go symbol, return its package or NULL if unknown.
> -   Space for the result is malloc'd, caller must free.  */
> +/* See go-lang.h.  */
>  
> -char *
> +gdb::unique_xmalloc_ptr<char>
>  go_symbol_package_name (const struct symbol *sym)
>  {
>    const char *mangled_name = sym->linkage_name ();
> @@ -393,8 +392,7 @@ go_symbol_package_name (const struct symbol *sym)
>    const char *method_type_package_name;
>    const char *method_type_object_name;
>    int method_type_is_pointer;
> -  char *name_buf;
> -  char *result;
> +  gdb::unique_xmalloc_ptr<char> name_buf;
>  
>    gdb_assert (sym->language () == language_go);
>    name_buf = unpack_mangled_go_symbol (mangled_name,
> @@ -405,15 +403,12 @@ go_symbol_package_name (const struct symbol *sym)
>    /* Some Go symbols don't have mangled form we interpret (yet).  */
>    if (name_buf == NULL)
>      return NULL;
> -  result = xstrdup (package_name);
> -  xfree (name_buf);
> -  return result;
> +  return make_unique_xstrdup (package_name);
>  }
>  
> -/* Return the package that BLOCK is in, or NULL if there isn't one.
> -   Space for the result is malloc'd, caller must free.  */
> +/* See go-lang.h.  */
>  
> -char *
> +gdb::unique_xmalloc_ptr<char>
>  go_block_package_name (const struct block *block)
>  {
>    while (block != NULL)
> @@ -422,7 +417,8 @@ go_block_package_name (const struct block *block)
>  
>        if (function != NULL)
>  	{
> -	  char *package_name = go_symbol_package_name (function);
> +	  gdb::unique_xmalloc_ptr<char> package_name
> +	    = go_symbol_package_name (function);
>  
>  	  if (package_name != NULL)
>  	    return package_name;
> diff --git a/gdb/go-lang.h b/gdb/go-lang.h
> index 1820b4c9658..877b6175534 100644
> --- a/gdb/go-lang.h
> +++ b/gdb/go-lang.h
> @@ -63,9 +63,14 @@ extern const char *go_main_name (void);
>  
>  extern enum go_type go_classify_struct_type (struct type *type);
>  
> -extern char *go_symbol_package_name (const struct symbol *sym);
> -
> -extern char *go_block_package_name (const struct block *block);
> +/* Given a Go symbol, return its package or NULL if unknown.  */
> +extern gdb::unique_xmalloc_ptr<char> go_symbol_package_name
> +     (const struct symbol *sym);
> +
> +/* Return the package that BLOCK is in, or NULL if there isn't
> +   one.  */
> +extern gdb::unique_xmalloc_ptr<char> go_block_package_name
> +     (const struct block *block);

Maybe replace NULL with nullptr in these comment.  But otherwise, this
all looks great.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew

>  
>  extern const struct builtin_go_type *builtin_go_type (struct gdbarch *);
>  
>
> -- 
> 2.39.1

Re: [PATCH 1/2] Avoid manual memory management in go-lang.c

[Tom Tromey]

>> +/* Given a Go symbol, return its package or NULL if unknown.  */
>> +extern gdb::unique_xmalloc_ptr<char> go_symbol_package_name
>> +     (const struct symbol *sym);
>> +
>> +/* Return the package that BLOCK is in, or NULL if there isn't
>> +   one.  */
>> +extern gdb::unique_xmalloc_ptr<char> go_block_package_name
>> +     (const struct block *block);

Andrew> Maybe replace NULL with nullptr in these comment.  But otherwise, this
Andrew> all looks great.

I've done this, thank you.

Tom

[PATCH 2/2] Fix crash in go_symbol_package_name

[Tom Tromey]

go_symbol_package_name package name asserts that it is only passed a
Go symbol, but this is not enforced by one caller.  It seems simplest
to just check and return early in this case.

Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=17876
---
 gdb/go-lang.c                       |  3 ++-
 gdb/testsuite/gdb.go/no-package.exp | 31 +++++++++++++++++++++++++++++++
 2 files changed, 33 insertions(+), 1 deletion(-)

diff --git a/gdb/go-lang.c b/gdb/go-lang.c
index f9176ace71d..bbf80af1f5c 100644
--- a/gdb/go-lang.c
+++ b/gdb/go-lang.c
@@ -394,7 +394,8 @@ go_symbol_package_name (const struct symbol *sym)
   int method_type_is_pointer;
   gdb::unique_xmalloc_ptr<char> name_buf;
 
-  gdb_assert (sym->language () == language_go);
+  if (sym->language () != language_go)
+    return nullptr;
   name_buf = unpack_mangled_go_symbol (mangled_name,
 				       &package_name, &object_name,
 				       &method_type_package_name,
diff --git a/gdb/testsuite/gdb.go/no-package.exp b/gdb/testsuite/gdb.go/no-package.exp
new file mode 100644
index 00000000000..3b39bc3220d
--- /dev/null
+++ b/gdb/testsuite/gdb.go/no-package.exp
@@ -0,0 +1,31 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2023 Free Software Foundation, Inc.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+# Regression test for a crash in go_symbol_package_name.
+
+load_lib "go.exp"
+
+require allow_go_tests support_go_compile !use_gdb_stub
+
+standard_testfile integers.go
+
+if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} {debug go}]} {
+    return -1
+}
+
+# The bug was that stopping in _start would crash.
+runto "*_start" message

-- 
2.39.1

Re: [PATCH 2/2] Fix crash in go_symbol_package_name

[Andrew Burgess]

Tom Tromey <tom@tromey.com> writes:

> go_symbol_package_name package name asserts that it is only passed a
> Go symbol, but this is not enforced by one caller.  It seems simplest
> to just check and return early in this case.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=17876
> ---
>  gdb/go-lang.c                       |  3 ++-
>  gdb/testsuite/gdb.go/no-package.exp | 31 +++++++++++++++++++++++++++++++
>  2 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/go-lang.c b/gdb/go-lang.c
> index f9176ace71d..bbf80af1f5c 100644
> --- a/gdb/go-lang.c
> +++ b/gdb/go-lang.c
> @@ -394,7 +394,8 @@ go_symbol_package_name (const struct symbol *sym)
>    int method_type_is_pointer;
>    gdb::unique_xmalloc_ptr<char> name_buf;
>  
> -  gdb_assert (sym->language () == language_go);
> +  if (sym->language () != language_go)
> +    return nullptr;

I think the comment for this function in go-lang.h can be updated.  The
comment claims that this function takes a Go symbol, when we now take
any symbol.

Looks fine with that updated.

Reviewed-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew


>    name_buf = unpack_mangled_go_symbol (mangled_name,
>  				       &package_name, &object_name,
>  				       &method_type_package_name,
> diff --git a/gdb/testsuite/gdb.go/no-package.exp b/gdb/testsuite/gdb.go/no-package.exp
> new file mode 100644
> index 00000000000..3b39bc3220d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.go/no-package.exp
> @@ -0,0 +1,31 @@
> +# This testcase is part of GDB, the GNU debugger.
> +
> +# Copyright 2023 Free Software Foundation, Inc.
> +#
> +# This program is free software; you can redistribute it and/or modify
> +# it under the terms of the GNU General Public License as published by
> +# the Free Software Foundation; either version 3 of the License, or
> +# (at your option) any later version.
> +#
> +# This program is distributed in the hope that it will be useful,
> +# but WITHOUT ANY WARRANTY; without even the implied warranty of
> +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +# GNU General Public License for more details.
> +#
> +# You should have received a copy of the GNU General Public License
> +# along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +
> +# Regression test for a crash in go_symbol_package_name.
> +
> +load_lib "go.exp"
> +
> +require allow_go_tests support_go_compile !use_gdb_stub
> +
> +standard_testfile integers.go
> +
> +if {[prepare_for_testing "failed to prepare" ${testfile} ${srcfile} {debug go}]} {
> +    return -1
> +}
> +
> +# The bug was that stopping in _start would crash.
> +runto "*_start" message
>
> -- 
> 2.39.1

Re: [PATCH 2/2] Fix crash in go_symbol_package_name

[Tom Tromey]

Andrew> I think the comment for this function in go-lang.h can be updated.  The
Andrew> comment claims that this function takes a Go symbol, when we now take
Andrew> any symbol.

Andrew> Looks fine with that updated.

I made this change, thanks.
I'm going to check these in soon.

Tom