Re: [PATCH] debuginfod-support.c: Replace globals with user_data

Aaron Merey
2020-08-12T21:40:03Z

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On Sat, Aug 1, 2020 at 10:45 AM Simon Marchi <simark@simark.ca> wrote:
>
> > From 1913317cb95d02c3244e5d91b7b59e33cfe991c5 Mon Sep 17 00:00:00 2001
> > From: Aaron Merey <amerey@redhat.com>
> > Date: Fri, 31 Jul 2020 18:25:48 -0400
> > Subject: [PATCH] debuginfod-support.c: Replace globals with user_data
> >
> > Store query information in user_data struct instead of global
> > variables. Also include DEBUGINFOD_CFLAGS in INTERNAL_CFLAG_BASE.
>
> The DEBUGINFOD_CFLAGS change looks good, but it's unrelated to the topic of this patch,
> please make it its own patch, with its own justification.
>
> > diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
> > index f4a227b040..9325bf8651 100644
> > --- a/gdb/debuginfod-support.c
> > +++ b/gdb/debuginfod-support.c
> > @@ -43,29 +43,39 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
> > #else
> > #include <elfutils/debuginfod.h>
> >
> > -/* TODO: Use debuginfod API extensions instead of these globals. */
> > -static std::string desc;
> > -static std::string fname;
> > -static bool has_printed;
> > +struct user_data
> > +{
> > + std::string desc;
> > + std::string fname;
> > + bool has_printed;
> > +
> > + user_data (std::string desc, std::string fname, bool has_printed)
> > + : desc (desc), fname (fname), has_printed (has_printed)
> > + { }
>
> Put the constructor before the fields. Make the fields const if they are not intended
> to be changed once the object has been created.
>
> Using `std::string` causes unnecessary copying to happen. Just use `const char *`
> (`const char * const` for the fields) or gdb::string_view, if you want to be more
> generic (but all callers are `const char *`, so it's not really necessary). That's
> assuming that the lifetime of those strings will always be longer than the lifetime
> of the debuginfo client. I think that's the case, since the debug info client is
> always created and destroyed in the same function.
>
> > +};
> >
> > static int
> > progressfn (debuginfod_client *c, long cur, long total)
> > {
> > + struct user_data *data = static_cast<user_data*> (debuginfod_get_user_data (c));
>
> This line is too long, just skip the `struct` keyword and you'll be fine. Also, space
> before `*`.
>
> > +
> > if (check_quit_flag ())
> > {
> > printf_filtered ("Cancelling download of %s %ps...\n",
> > - desc.c_str (),
> > - styled_string (file_name_style.style (), fname.c_str ()));
> > + data->desc.c_str (),
> > + styled_string (file_name_style.style (),
> > + data->fname.c_str ()));
> > return 1;
> > }
> >
> > - if (!has_printed && total != 0)
> > + if (! data->has_printed && total != 0)
>
> Remove space after `!`.

Hi Simon,

Thanks for the review, I've updated the patch and moved the Makefile.in
change to a separate patch.

Aaron

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From 922179058218a82f9b74e328249e67244adae3fc Mon Sep 17 00:00:00 2001
From: Aaron Merey <amerey@redhat.com>
Date: Wed, 12 Aug 2020 17:23:42 -0400
Subject: [PATCH 2/2] debuginfod-support.c: Replace globals with user_data

Store query information in user_data struct instead of global variables.

gdb/ChangeLog:

* debuginfod-support.c: Replace global variables with user_data.
---
gdb/ChangeLog | 4 ++++
gdb/debuginfod-support.c | 38 ++++++++++++++++++++++----------------
2 files changed, 26 insertions(+), 16 deletions(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 0e035e233f..ad54c49864 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,7 @@
+2020-08-12 Aaron Merey <amerey@redhat.com>
+
+ * debuginfod-support.c: Replace global variables with user_data.
+
2020-08-12 Aaron Merey <amerey@redhat.com>

* Makefile.in (DEBUGINFOD_CFLAGS, DEBUGINFOD_LIBS): New variables.
diff --git a/gdb/debuginfod-support.c b/gdb/debuginfod-support.c
index f4a227b040..3f51aaaf43 100644
--- a/gdb/debuginfod-support.c
+++ b/gdb/debuginfod-support.c
@@ -43,29 +43,37 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
#else
#include <elfutils/debuginfod.h>

-/* TODO: Use debuginfod API extensions instead of these globals. */
-static std::string desc;
-static std::string fname;
-static bool has_printed;
+struct user_data
+{
+ user_data (const char *desc, const char *fname, bool has_printed)
+ : desc (desc), fname (fname), has_printed (has_printed)
+ { }
+
+ const char * const desc;
+ const char * const fname;
+ bool has_printed;
+};

static int
progressfn (debuginfod_client *c, long cur, long total)
{
+ user_data *data = static_cast<user_data *> (debuginfod_get_user_data (c));
+
if (check_quit_flag ())
{
printf_filtered ("Cancelling download of %s %ps...\n",
- desc.c_str (),
- styled_string (file_name_style.style (), fname.c_str ()));
+ data->desc,
+ styled_string (file_name_style.style (), data->fname));
return 1;
}

- if (!has_printed && total != 0)
+ if (!data->has_printed && total != 0)
{
/* Print this message only once. */
- has_printed = true;
+ data->has_printed = true;
printf_filtered ("Downloading %s %ps...\n",
- desc.c_str (),
- styled_string (file_name_style.style (), fname.c_str ()));
+ data->desc,
+ styled_string (file_name_style.style (), data->fname));
}

return 0;
@@ -98,10 +106,9 @@ debuginfod_source_query (const unsigned char *build_id,
if (c == nullptr)
return scoped_fd (-ENOMEM);

- desc = std::string ("source file");
- fname = std::string (srcpath);
- has_printed = false;
+ struct user_data data ("source file", srcpath, false);

+ debuginfod_set_user_data (c, &data);
scoped_fd fd (debuginfod_find_source (c,
build_id,
build_id_len,
@@ -136,11 +143,10 @@ debuginfod_debuginfo_query (const unsigned char *build_id,
if (c == nullptr)
return scoped_fd (-ENOMEM);

- desc = std::string ("separate debug info for");
- fname = std::string (filename);
- has_printed = false;
char *dname = nullptr;
+ struct user_data data ("separate debug info for", filename, false);

+ debuginfod_set_user_data (c, &data);
scoped_fd fd (debuginfod_find_debuginfo (c, build_id, build_id_len, &dname));

if (fd.get () < 0 && fd.get () != -ENOENT)
--
2.25.4