From: Steve Baird <ba...@adacore.com>
The -gnatw.h option enables warnings about "gaps" in record layout
specifications. In the case of a "partial" layout specification, where the
locations of some components are left unspecified, the resulting warnings
may be incomplete or incorrect. Document this implementation limitation.
gcc/ada/
* doc/gnat_ugn/building_executable_programs_with_gnat.rst: Improve
the description of how the -gnatw.h switch interacts with
"partial" record layout specifications (i.e., specifications where
the locations of some components are left unspecified).
* gnat_ugn.texi: Regenerate.
Tested on x86_64-pc-linux-gnu, committed on master.
---
.../building_executable_programs_with_gnat.rst | 9 +++++++--
gcc/ada/gnat_ugn.texi | 11 ++++++++---
2 files changed, 15 insertions(+), 5 deletions(-)
diff --git a/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
index 87fb1087e42..fe0b567c2b9 100644
--- a/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
+++ b/gcc/ada/doc/gnat_ugn/building_executable_programs_with_gnat.rst
@@ -3221,8 +3221,13 @@ of the pragma in the :title:`GNAT_Reference_manual`).
This switch activates warnings on component clauses in record
representation clauses that leave holes (gaps) in the record layout.
- If this warning option is active, then record representation clauses
- should specify a contiguous layout, adding unused fill fields if needed.
+ If a record representation clause does not specify a location for
+ every component of the record type, then the warnings generated (or not
+ generated) are unspecified. For example, there may be gaps for which
+ either no warning is generated or a warning is generated that
+ incorrectly describes the location of the gap. This undesirable situation
+ can sometimes be avoided by adding (and specifying the location for) unused
+ fill fields.
.. index:: -gnatw.H (gcc)
diff --git a/gcc/ada/gnat_ugn.texi b/gcc/ada/gnat_ugn.texi
index 2f43b4f71c8..12eb494d40d 100644
--- a/gcc/ada/gnat_ugn.texi
+++ b/gcc/ada/gnat_ugn.texi
@@ -19,7 +19,7 @@
@copying
@quotation
-GNAT User's Guide for Native Platforms , Nov 14, 2022
+GNAT User's Guide for Native Platforms , Nov 18, 2022
AdaCore
@@ -11305,8 +11305,13 @@ This switch suppresses warnings on hiding declarations.
This switch activates warnings on component clauses in record
representation clauses that leave holes (gaps) in the record layout.
-If this warning option is active, then record representation clauses
-should specify a contiguous layout, adding unused fill fields if needed.
+If a record representation clause does not specify a location for
+every component of the record type, then the warnings generated (or not
+generated) are unspecified. For example, there may be gaps for which
+either no warning is generated or a warning is generated that
+incorrectly describes the location of the gap. This undesirable situation
+can sometimes be avoided by adding (and specifying the location for) unused
+fill fields.
@end table
@geindex -gnatw.H (gcc)
--
2.34.1
