[binutils-gdb] gdb: update Type.fields doc based on actual GDB behavior

[binutils-gdb] gdb: update Type.fields doc based on actual GDB behavior

[Simon Marchi]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=fa94b3a7c817a5e6615b24eeb3ac569b70af7e81

commit fa94b3a7c817a5e6615b24eeb3ac569b70af7e81
Author: Simon Marchi <simon.marchi@polymtl.ca>
Date:   Tue May 4 22:19:05 2021 -0400

    gdb: update Type.fields doc based on actual GDB behavior
    
    I noticed two errors in the Type.fields documentation:
    
    1. It is possible to call `fields` on an array type, in which case it
       returns one field representing the array's range.  It is not
       mentioned.
    
    2. When calling `fields` on a type that doesn't have fields (by nature,
       like an int), GDB raises a TypeError.  It does not return an empty
       sequence, as currently documented.
    
    Fix these, and change the text into a bullet list.  I find it easier to
    read than one big paragraph.
    
    The first issue is already tested in gdb.python/py-type.exp, but the
    second one doesn't seem tested.  Add a test in gdb.python/py-type.exp
    for it.
    
    gdb/doc/ChangeLog:
    
            * python.texi (Types In Python): Re-organize Type.fields doc.
            Mention handling of array types.  Correct doc for when calling
            the method on another type.
    
    gdb/testsuite/ChangeLog:
    
            * gdb.python/py-type.exp (test_fields): Test calling fields on
            an int type.
    
    Change-Id: I11c688177504cb070b81a4446ac91dec50b56a22

Diff:
---
 gdb/doc/ChangeLog                    |  6 ++++++
 gdb/doc/python.texi                  | 32 ++++++++++++++++++++++++++------
 gdb/testsuite/ChangeLog              |  5 +++++
 gdb/testsuite/gdb.python/py-type.exp |  3 +++
 4 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/gdb/doc/ChangeLog b/gdb/doc/ChangeLog
index d801d76dceb..ec961d232d1 100644
--- a/gdb/doc/ChangeLog
+++ b/gdb/doc/ChangeLog
@@ -1,3 +1,9 @@
+2021-05-04  Simon Marchi  <simon.marchi@polymtl.ca>
+
+	* python.texi (Types In Python): Re-organize Type.fields doc.
+	Mention handling of array types.  Correct doc for when calling
+	the method on another type.
+
 2021-04-28  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.texinfo (Initialization Files): Use @env when referencing
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index 20d65742964..482d328de44 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -1163,12 +1163,32 @@ there is no associated objfile.
 The following methods are provided:
 
 @defun Type.fields ()
-For structure and union types, this method returns the fields.  Range
-types have two fields, the minimum and maximum values.  Enum types
-have one field per enum constant.  Function and method types have one
-field per parameter.  The base types of C@t{++} classes are also
-represented as fields.  If the type has no fields, or does not fit
-into one of these categories, an empty sequence will be returned.
+
+Return the fields of this type.  The behavior depends on the type code:
+
+@itemize @bullet
+
+@item
+For structure and union types, this method returns the fields.
+
+@item
+Range types have two fields, the minimum and maximum values.
+
+@item
+Enum types have one field per enum constant.
+
+@item
+Function and method types have one field per parameter.  The base types of
+C@t{++} classes are also represented as fields.
+
+@item
+Array types have one field representing the array's range.
+
+@item
+If the type does not fit into one of these categories, a @code{TypeError}
+is raised.
+
+@end itemize
 
 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
 @table @code
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index 32eba3663a7..326ba47961f 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2021-05-04  Simon Marchi  <simon.marchi@polymtl.ca>
+
+	* gdb.python/py-type.exp (test_fields): Test calling fields on
+	an int type.
+
 2021-05-04  Simon Marchi  <simon.marchi@efficios.com>
 
 	* gdb.python/flexible-array-member.exp: Adjust expected range
diff --git a/gdb/testsuite/gdb.python/py-type.exp b/gdb/testsuite/gdb.python/py-type.exp
index 5c0c4f5706f..733b25d3210 100644
--- a/gdb/testsuite/gdb.python/py-type.exp
+++ b/gdb/testsuite/gdb.python/py-type.exp
@@ -175,6 +175,9 @@ proc test_fields {lang} {
     gdb_test "python print (len (gdb.parse_and_eval ('a_function').type.fields ()))" "2"
     gdb_test "python print (gdb.parse_and_eval ('a_function').type.fields ()\[0\].type)" "int"
     gdb_test "python print (gdb.parse_and_eval ('a_function').type.fields ()\[1\].type)" "char"
+
+    # Test calling `fields` on a non-aggregate type.
+    gdb_test "python gdb.lookup_type('int').fields()" "TypeError: Type is not a structure, union, enum, or function type.*"
   }
 }