[binutils-gdb] Add a comment briefly explaining partial symbols

[Christian Biesinger]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=4ee94178afbe062bc244d28595f86d63633a7af7

commit 4ee94178afbe062bc244d28595f86d63633a7af7
Author: Christian Biesinger <cbiesinger@google.com>
Date:   Wed Jul 31 17:10:50 2019 -0500

    Add a comment briefly explaining partial symbols
    
    Based on an explanation by tromey on IRC.
    
    gdb/ChangeLog:
    
    2019-08-05  Christian Biesinger  <cbiesinger@google.com>
    
    	* objfiles.h (objfile): Add a comment describing partial symbols.

Diff:
---
 gdb/ChangeLog  | 4 ++++
 gdb/objfiles.h | 8 +++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0d324a5..da1d636 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2019-08-05  Christian Biesinger  <cbiesinger@google.com>
+
+	* objfiles.h (objfile): Add a comment describing partial symbols.
+
 2019-08-05  Tom Tromey  <tromey@adacore.com>
 
 	* compile/compile.c (_initialize_compile): Use _(), not N_().
diff --git a/gdb/objfiles.h b/gdb/objfiles.h
index a0c106b..239aba2 100644
--- a/gdb/objfiles.h
+++ b/gdb/objfiles.h
@@ -382,7 +382,13 @@ private:
    2.  Additional symbol files added by the add-symbol-file command,
    3.  Shared library objfiles, added by ADD_SOLIB,  4.  symbol files
    for modules that were loaded when GDB attached to a remote system
-   (see remote-vx.c).  */
+   (see remote-vx.c).
+
+   GDB typically reads symbols twice -- first an initial scan which just
+   reads "partial symbols"; these are partial information for the
+   static/global symbols in a symbol file.  When later looking up symbols,
+   objfile->sf->qf->lookup_symbol is used to check if we only have a partial
+   symbol and if so, read and expand the full compunit.  */
 
 struct objfile
 {