[binutils-gdb] set/show python dont-write-bytecode fixes

[binutils-gdb] set/show python dont-write-bytecode fixes

[Kevin Buettner]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=24d2cbc42ccf08dba79394635db3be084eed9062

commit 24d2cbc42ccf08dba79394635db3be084eed9062
Author: Kevin Buettner <kevinb@redhat.com>
Date:   Mon Jul 25 12:04:10 2022 -0700

    set/show python dont-write-bytecode fixes
    
    GDB uses the environment variable PYTHONDONTWRITEBYTECODE to
    determine whether or not to write the result of byte-compiling
    python modules when the "python dont-write-bytecode" setting
    is "auto".  Simon noticed that GDB's implementation doesn't
    follow the Python documentation.
    
    At present, GDB only checks for the existence of this environment
    variable.  That is not sufficient though.  Regarding
    PYTHONDONTWRITEBYTECODE, this document...
    
        https://docs.python.org/3/using/cmdline.html
    
    ...says:
    
        If this is set to a non-empty string, Python won't try to write
        .pyc files on the import of source modules.
    
    This commit fixes GDB's handling of PYTHONDONTWRITEBYTECODE by adding
    an empty string check.
    
    This commit also corrects the set/show command documentation for
    "python dont-write-bytecode".  The current doc was just a copy
    of that for set/show python ignore-environment.
    
    During his review of an earlier version of this patch, Eli Zaretskii
    asked that the help text that I proposed for "set/show python
    dont-write-bytecode" be expanded.  I've done that in addition to
    clarifying the documentation of this option in the GDB manual.

Diff:
---
 gdb/doc/python.texi |  9 +++++++--
 gdb/python/python.c | 32 +++++++++++++++++++++++++-------
 2 files changed, 32 insertions(+), 9 deletions(-)

diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index eeb847aeaa8..cdf7db91602 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -134,9 +134,14 @@ initialized early during @value{GDBN}'s startup process, then this
 option must be placed into the early initialization file
 (@pxref{Initialization Files}) to have the desired effect.
 
-By default this option is set to @samp{auto}, in this mode Python will
-check the environment variable @env{PYTHONDONTWRITEBYTECODE} to see
+By default this option is set to @samp{auto}.  In this mode, provided
+the @code{python ignore-environment} setting is @samp{off}, the
+environment variable @env{PYTHONDONTWRITEBYTECODE} is examined to see
 if it should write out byte-code or not.
+@env{PYTHONDONTWRITEBYTECODE} is considered to be off/disabled either
+when set to the empty string or when the environment variable doesn't
+exist.  All other settings, including those which don't seem to make
+sense, indicate that it's on/enabled.
 
 This option is equivalent to passing @option{-B} to the real
 @command{python} executable.
diff --git a/gdb/python/python.c b/gdb/python/python.c
index c7d4157b70c..7997bee2c69 100644
--- a/gdb/python/python.c
+++ b/gdb/python/python.c
@@ -1866,8 +1866,15 @@ python_write_bytecode ()
   int wbc = 0;
 
   if (python_dont_write_bytecode == AUTO_BOOLEAN_AUTO)
-    wbc = (!python_ignore_environment
-	    && getenv ("PYTHONDONTWRITEBYTECODE") != nullptr) ? 0 : 1;
+    {
+      if (python_ignore_environment)
+	wbc = 1;
+      else
+	{
+	  const char *pdwbc = getenv ("PYTHONDONTWRITEBYTECODE");
+	  wbc = (pdwbc == nullptr || pdwbc[0] == '\0') ? 1 : 0;
+	}
+    }
   else
     wbc = python_dont_write_bytecode == AUTO_BOOLEAN_TRUE ? 0 : 1;
 
@@ -2346,11 +2353,22 @@ python executable."),
 
   add_setshow_auto_boolean_cmd ("dont-write-bytecode", no_class,
 				&python_dont_write_bytecode, _("\
-Set whether the Python interpreter should ignore environment variables."), _(" \
-Show whether the Python interpreter showlist ignore environment variables."), _(" \
-When enabled GDB's Python interpreter will ignore any Python related\n	\
-flags in the environment.  This is equivalent to passing `-E' to a\n	\
-python executable."),
+Set whether the Python interpreter should avoid byte-compiling python modules."), _("\
+Show whether the Python interpreter should avoid byte-compiling python modules."), _("\
+When enabled, GDB's embedded Python interpreter won't byte-compile python\n\
+modules.  In order to take effect, this setting must be enabled in an early\n\
+initialization file, i.e. those run via the --early-init-eval-command or\n\
+-eix command line options.  A 'set python dont-write-bytecode on' command\n\
+can also be issued directly from the GDB command line via the\n\
+--early-init-eval-command or -eiex command line options.\n\
+\n\
+This setting defaults to 'auto'.  In this mode, provided the 'python\n\
+ignore-environment' setting is 'off', the environment variable\n\
+PYTHONDONTWRITEBYTECODE is examined to determine whether or not to\n\
+byte-compile python modules.  PYTHONDONTWRITEBYTECODE is considered to be\n\
+off/disabled either when set to the empty string or when the\n\
+environment variable doesn't exist.  All other settings, including those\n\
+which don't seem to make sense, indicate that it's on/enabled."),
 				set_python_dont_write_bytecode,
 				show_python_dont_write_bytecode,
 				&user_set_python_list,