[PATCH] gdb: use std::vector instead of alloca in core_target::get_core_register_section

Simon Marchi
2020-01-12T20:17:34Z

As I was trying to compile gdb for an m68k host, I got this error:

CXX corelow.o
In file included from /binutils-gdb/gdb/gdbsupport/common-defs.h:120,
from /binutils-gdb/gdb/defs.h:28,
from /binutils-gdb/gdb/corelow.c:20:
/binutils-gdb/gdb/corelow.c: In member function 'void core_target::get_core_register_section(regcache*, const regset*, const char*, int, int, const char*, bool)':
/binutils-gdb/gdb/../include/libiberty.h:727:36: error: 'alloca' bound is unknown [-Werror=alloca-larger-than=]
727 | # define alloca(x) __builtin_alloca(x)
| ~~~~~~~~~~~~~~~~^~~
/binutils-gdb/gdb/corelow.c:625:23: note: in expansion of macro 'alloca'
625 | contents = (char *) alloca (size);
| ^~~~~~

We are using alloca to hold the contents of a the core register
sections. These sections are typically fairly small, but there is no
realy guarantee, so I think it would be more reasonable to just use
dynamic allocation here.

gdb/ChangeLog:

* corelow.c (core_target::get_core_register_section): Use
std::vector instead of alloca.
---
gdb/corelow.c | 9 ++++-----
1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/gdb/corelow.c b/gdb/corelow.c
index c53bf1df8fd8..e7efa652d62a 100644
--- a/gdb/corelow.c
+++ b/gdb/corelow.c
@@ -594,7 +594,6 @@ core_target::get_core_register_section (struct regcache *regcache,
{
struct bfd_section *section;
bfd_size_type size;
- char *contents;
bool variable_size_section = (regset != NULL
&& regset->flags & REGSET_VARIABLE_SIZE);

@@ -622,8 +621,8 @@ core_target::get_core_register_section (struct regcache *regcache,
section_name.c_str ());
}

- contents = (char *) alloca (size);
- if (! bfd_get_section_contents (core_bfd, section, contents,
+ std::vector<char> contents (size);
+ if (! bfd_get_section_contents (core_bfd, section, contents.data (),
(file_ptr) 0, size))
{
warning (_("Couldn't read %s registers from `%s' section in core file."),
@@ -633,12 +632,12 @@ core_target::get_core_register_section (struct regcache *regcache,

if (regset != NULL)
{
- regset->supply_regset (regset, regcache, -1, contents, size);
+ regset->supply_regset (regset, regcache, -1, contents.data (), size);
return;
}

gdb_assert (m_core_vec != nullptr);
- m_core_vec->core_read_registers (regcache, contents, size, which,
+ m_core_vec->core_read_registers (regcache, contents.data (), size, which,
(CORE_ADDR) bfd_section_vma (section));
}

--
2.24.1