[1/2] gdbsupport, gdb: add read_text_file_to_string, use it in linux_common_core_of_thread
Commit Message
I would like to add more code to nat/linux-osdata.c that reads an entire
file from /proc or /sys and processes it as a string afterwards. I
would like to avoid duplicating the somewhat error-prone code that reads
an entire file to a buffer. I think we should have a utility function
that does that.
Add read_file_to_string to gdbsupport/filestuff.{c,h}, and make
linux_common_core_of_thread use it. I want to make the new function
return an std::string, and because strtok doesn't play well with
std::string (it requires a `char *`, std::string::c_str returns a `const
char *`), change linux_common_core_of_thread to use std::string methods
instead.
Change-Id: I1793fda72a82969c28b944a84acb953f74c9230a
---
gdb/nat/linux-osdata.c | 52 +++++++++++++++++------------------------
gdbsupport/filestuff.cc | 35 +++++++++++++++++++++++++++
gdbsupport/filestuff.h | 2 ++
3 files changed, 58 insertions(+), 31 deletions(-)
Comments
>>>>> "Simon" == Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:
Simon> I would like to add more code to nat/linux-osdata.c that reads an entire
Simon> file from /proc or /sys and processes it as a string afterwards. I
Simon> would like to avoid duplicating the somewhat error-prone code that reads
Simon> an entire file to a buffer. I think we should have a utility function
Simon> that does that.
Makes sense. source_cache::get_plain_source_lines could use this btw,
though it would need some change for error reporting.
Simon> +
Simon> +gdb::optional<std::string>
Simon> +read_text_file_to_string (const char *path)
Should have a comment.
Simon> +extern gdb::optional<std::string> read_text_file_to_string (const char *path);
Here too.
Tom
On 11/8/22 12:13, Tom Tromey wrote:
>>>>>> "Simon" == Simon Marchi via Gdb-patches <gdb-patches@sourceware.org> writes:
>
> Simon> I would like to add more code to nat/linux-osdata.c that reads an entire
> Simon> file from /proc or /sys and processes it as a string afterwards. I
> Simon> would like to avoid duplicating the somewhat error-prone code that reads
> Simon> an entire file to a buffer. I think we should have a utility function
> Simon> that does that.
>
> Makes sense. source_cache::get_plain_source_lines could use this btw,
> though it would need some change for error reporting.
Ok, although it would need a bit of refactoring, because that uses
open_source_file, which returns a scoped_fd.
I also spotted xml_fetch_content_from_file. The problem here is that it
returns a gdb::char_vector, not an std::string. To change it, we would
have to change to std::string all the way to target_read_stralloc. I
think it would be nice (it's nicer to use std::string for strings than
gdb::char_vector), but a bit too much just for this patch.
>
> Simon> +
> Simon> +gdb::optional<std::string>
> Simon> +read_text_file_to_string (const char *path)
>
> Should have a comment.
>
>
> Simon> +extern gdb::optional<std::string> read_text_file_to_string (const char *path);
>
> Here too.
Oops, forgot. Does that look good to you?
diff --git a/gdbsupport/filestuff.cc b/gdbsupport/filestuff.cc
index d003a7f39c4..cf5fb13bd0c 100644
--- a/gdbsupport/filestuff.cc
+++ b/gdbsupport/filestuff.cc
@@ -502,6 +502,8 @@ mkdir_recursive (const char *dir)
}
}
+/* See gdbsupport/filestuff.h. */
+
gdb::optional<std::string>
read_text_file_to_string (const char *path)
{
diff --git a/gdbsupport/filestuff.h b/gdbsupport/filestuff.h
index 3932710b5dc..33362901ab8 100644
--- a/gdbsupport/filestuff.h
+++ b/gdbsupport/filestuff.h
@@ -129,6 +129,8 @@ extern bool is_regular_file (const char *name, int *errno_ptr);
extern bool mkdir_recursive (const char *dir);
+/* Read the entire content of file PATH into an std::string. */
+
extern gdb::optional<std::string> read_text_file_to_string (const char *path);
#endif /* COMMON_FILESTUFF_H */
Simon
Simon> Oops, forgot. Does that look good to you?
Yes, thank you.
Tom
On 11/8/22 16:48, Tom Tromey wrote:
> Simon> Oops, forgot. Does that look good to you?
>
> Yes, thank you.
>
> Tom
Thanks, pushed both patches.
Simon
@@ -62,49 +62,39 @@ int
linux_common_core_of_thread (ptid_t ptid)
{
char filename[sizeof ("/proc//task//stat") + 2 * MAX_PID_T_STRLEN];
- char *content = NULL;
- char *p;
- char *ts = 0;
- int content_read = 0;
- int i;
int core;
sprintf (filename, "/proc/%lld/task/%lld/stat",
(PID_T) ptid.pid (), (PID_T) ptid.lwp ());
- gdb_file_up f = gdb_fopen_cloexec (filename, "r");
- if (!f)
- return -1;
- for (;;)
- {
- int n;
- content = (char *) xrealloc (content, content_read + 1024);
- n = fread (content + content_read, 1, 1024, f.get ());
- content_read += n;
- if (n < 1024)
- {
- content[content_read] = '\0';
- break;
- }
- }
+ gdb::optional<std::string> content = read_text_file_to_string (filename);
+ if (!content.has_value ())
+ return -1;
/* ps command also relies on no trailing fields ever contain ')'. */
- p = strrchr (content, ')');
- if (p != NULL)
- p++;
+ std::string::size_type pos = content->find_last_of (')');
+ if (pos == std::string::npos)
+ return -1;
/* If the first field after program name has index 0, then core number is
- the field with index 36. There's no constant for that anywhere. */
- if (p != NULL)
- p = strtok_r (p, " ", &ts);
- for (i = 0; p != NULL && i != 36; ++i)
- p = strtok_r (NULL, " ", &ts);
+ the field with index 36 (so, the 37th). There's no constant for that
+ anywhere. */
+ for (int i = 0; i < 37; ++i)
+ {
+ /* Find separator. */
+ pos = content->find_first_of (' ', pos);
+ if (pos == std::string::npos)
+ return {};
+
+ /* Find beginning of field. */
+ pos = content->find_first_not_of (' ', pos);
+ if (pos == std::string::npos)
+ return {};
+ }
- if (p == NULL || sscanf (p, "%d", &core) == 0)
+ if (sscanf (&(*content)[pos], "%d", &core) == 0)
core = -1;
- xfree (content);
-
return core;
}
@@ -501,3 +501,38 @@ mkdir_recursive (const char *dir)
component_start = component_end;
}
}
+
+gdb::optional<std::string>
+read_text_file_to_string (const char *path)
+{
+ gdb_file_up file = gdb_fopen_cloexec (path, "r");
+ if (file == nullptr)
+ return {};
+
+ std::string res;
+ for (;;)
+ {
+ std::string::size_type start_size = res.size ();
+ constexpr int chunk_size = 1024;
+
+ /* Resize to accomodate CHUNK_SIZE bytes. */
+ res.resize (start_size + chunk_size);
+
+ int n = fread (&res[start_size], 1, chunk_size, file.get ());
+ if (n == chunk_size)
+ continue;
+
+ gdb_assert (n < chunk_size);
+
+ /* Less than CHUNK means EOF or error. If it's an error, return
+ no value. */
+ if (ferror (file.get ()))
+ return {};
+
+ /* Resize the string according to the data we read. */
+ res.resize (start_size + n);
+ break;
+ }
+
+ return res;
+}
@@ -129,4 +129,6 @@ extern bool is_regular_file (const char *name, int *errno_ptr);
extern bool mkdir_recursive (const char *dir);
+extern gdb::optional<std::string> read_text_file_to_string (const char *path);
+
#endif /* COMMON_FILESTUFF_H */