warn if "source" fails to open the file when from_tty == 0

Consider the following example:

    % gdb -q -batch -ex 'source nonexistant-file'
    [nothing]

One would have at least expected the debugger to warn about
not finding the file, similar to the error shown when using
a more interactive mode. Eg:

    (gdb) source nonexistant-file
    nonexistant-file: No such file or directory.

Not raising an error appears to be intentional, presumably in order
to prevent this situation from stoping the execution of a GDB script.
But the lack of at least a warning makes it harder for a user to
diagnose any issue, if the file was expected to be there and readable.

This patch adds a warning in that case:

    % gdb -q -batch -ex 'source nonexistant-file'
    warning: nonexistant-file: No such file or directory.

gdb/ChangeLog:

        * utils.h (perror_warning_with_name): Add declaration.
        * utils.c (perror_warning_with_name): New function.
        * cli/cli-cmds.c (source_script_with_search): Add call to
        perror_warning_with_name if from_tty is nul.

gdb/testsuite/ChangeLog:

        * gdb.base/source-nofile.gdb: New file.
        * gdb.base/source.exp: Add two tests verifying the behavior when
        the "source" command is given a non-existant filename.

1 files changed, 2 insertions, 0 deletions

diff --git a/gdb/utils.h b/gdb/utils.h
index 3492f09..7ea0ff4 100644
--- a/gdb/utils.h
+++ b/gdb/utils.h
@@ -285,6 +285,8 @@ extern void throw_perror_with_name (enum errors errcode, const char *string)
   ATTRIBUTE_NORETURN;
 extern void perror_with_name (const char *) ATTRIBUTE_NORETURN;
 
+extern void perror_warning_with_name (const char *string);
+
 extern void print_sys_errmsg (const char *, int);
 
 /* Warnings and error messages.  */