From 3c3ae77e68a9032ef9f174bf6b1cc992b6a4cb35 Mon Sep 17 00:00:00 2001 From: Pedro Alves Date: Thu, 4 May 2017 15:14:37 +0100 Subject: [PATCH] Fix get_core_register_section leak, introduce thread_section_name This plugs a leak introduced in the previous change to get_core_register_section, which removed an xfree call that is actually necessary because the 'section_name' local is static. From [1] it looks like the reason the variable was made static to begin with, was just "laziness" to avoid having to think about freeing it on every function return path: https://sourceware.org/ml/gdb-patches/2005-03/msg00237.html The easiest to fix that nowadays is to use a std::string. I don't see a need to xstrdup the section name in the single-threaded case though, and also there's more than one place that computes a multi-threaded section name in the same way. So put the section name computation in a wrapper class with state. gdb/ChangeLog: 2017-05-04 Pedro Alves * corelow.c (thread_section_name): New class. (get_core_register_section, get_core_siginfo): Use it. --- gdb/ChangeLog | 5 ++++ gdb/corelow.c | 76 +++++++++++++++++++++++++++++++++++++++++------------------ 2 files changed, 58 insertions(+), 23 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index de4d90f..aeb83dd 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,8 @@ +2017-05-04 Pedro Alves + + * corelow.c (thread_section_name): New class. + (get_core_register_section, get_core_siginfo): Use it. + 2017-05-04 Andreas Arnez * corelow.c (sniff_core_bfd): Remove extra semicolon. diff --git a/gdb/corelow.c b/gdb/corelow.c index 2266f24..0aff02d 100644 --- a/gdb/corelow.c +++ b/gdb/corelow.c @@ -485,6 +485,51 @@ core_detach (struct target_ops *ops, const char *args, int from_tty) printf_filtered (_("No core file now.\n")); } +/* Build either a single-thread or multi-threaded section name for + PTID. + + If ptid's lwp member is zero, we want to do the single-threaded + thing: look for a section named NAME (as passed to the + constructor). If ptid's lwp member is non-zero, we'll want do the + multi-threaded thing: look for a section named "NAME/LWP", where + LWP is the shortest ASCII decimal representation of ptid's lwp + member. */ + +class thread_section_name +{ +public: + /* NAME is the single-threaded section name. If PTID represents an + LWP, then the build section name is "NAME/LWP", otherwise it's + just "NAME" unmodified. */ + thread_section_name (const char *name, ptid_t ptid) + { + if (ptid.lwp_p ()) + { + m_storage = string_printf ("%s/%ld", name, ptid.lwp ()); + m_section_name = m_storage.c_str (); + } + else + m_section_name = name; + } + + /* Return the computed section name. The result is valid as long as + this thread_section_name object is live. */ + const char *c_str () const + { return m_section_name; } + + /* Disable copy. */ + thread_section_name (const thread_section_name &) = delete; + void operator= (const thread_section_name &) = delete; + +private: + /* Either a pointer into M_STORAGE, or a pointer to the name passed + as parameter to the constructor. */ + const char *m_section_name; + /* If we need to build a new section name, this is where we store + it. */ + std::string m_storage; +}; + /* Try to retrieve registers from a section in core_bfd, and supply them to core_vec->core_read_registers, as the register set numbered WHICH. @@ -511,21 +556,15 @@ get_core_register_section (struct regcache *regcache, const char *human_name, int required) { - static char *section_name; struct bfd_section *section; bfd_size_type size; char *contents; bool variable_size_section = (regset != NULL && regset->flags & REGSET_VARIABLE_SIZE); - ptid_t ptid = regcache_get_ptid (regcache); - if (ptid_get_lwp (ptid)) - section_name = xstrprintf ("%s/%ld", name, - ptid_get_lwp (ptid)); - else - section_name = xstrdup (name); + thread_section_name section_name (name, regcache->ptid ()); - section = bfd_get_section_by_name (core_bfd, section_name); + section = bfd_get_section_by_name (core_bfd, section_name.c_str ()); if (! section) { if (required) @@ -537,13 +576,14 @@ get_core_register_section (struct regcache *regcache, size = bfd_section_size (core_bfd, section); if (size < min_size) { - warning (_("Section `%s' in core file too small."), section_name); + warning (_("Section `%s' in core file too small."), + section_name.c_str ()); return; } if (size != min_size && !variable_size_section) { warning (_("Unexpected size of section `%s' in core file."), - section_name); + section_name.c_str ()); } contents = (char *) alloca (size); @@ -551,7 +591,7 @@ get_core_register_section (struct regcache *regcache, (file_ptr) 0, size)) { warning (_("Couldn't read %s registers from `%s' section in core file."), - human_name, name); + human_name, section_name.c_str ()); return; } @@ -681,18 +721,8 @@ add_to_spuid_list (bfd *abfd, asection *asect, void *list_p) static LONGEST get_core_siginfo (bfd *abfd, gdb_byte *readbuf, ULONGEST offset, ULONGEST len) { - asection *section; - char *section_name; - const char *name = ".note.linuxcore.siginfo"; - - if (ptid_get_lwp (inferior_ptid)) - section_name = xstrprintf ("%s/%ld", name, - ptid_get_lwp (inferior_ptid)); - else - section_name = xstrdup (name); - - section = bfd_get_section_by_name (abfd, section_name); - xfree (section_name); + thread_section_name section_name (".note.linuxcore.siginfo", inferior_ptid); + asection *section = bfd_get_section_by_name (abfd, section_name.c_str ()); if (section == NULL) return -1; -- 2.7.4