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Determine endianness at a time when it doesn't inadvertantly clear gdb's wrap_buffer via gdb.execute. 

Summary:
I haven't managed a small reproduction for this bug, it involves
complicated and deeply nested data structures with a wide variety
of pretty printers. But in general, we shouldn't be combining
gdb's command line interface (via gdb.execute) with pretty-printers.

Subscribers: christof, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D68306

llvm-svn: 373402
This commit is contained in:
Sterling Augustine 2019-10-01 22:42:37 +00:00
parent 0da163a2cf
commit 9b36c1cf27
1 changed files with 11 additions and 7 deletions
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18
libcxx/utils/gdb/libcxx/printers.py
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@ -27,6 +27,7 @@ _void_pointer_type = gdb.lookup_type("void").pointer()
_long_int_type = gdb.lookup_type("unsigned long long")
_libcpp_big_endian = False
def addr_as_long(addr):
return int(addr.cast(_long_int_type))
@ -195,19 +196,14 @@ class StdStringPrinter(object):
field = short_field.type.fields()[1].type.fields()[0]
libcpp_abi_alternate_string_layout = field.name and "__padding" in field.name
# Strictly, this only tells us the current mode, not how libcxx was
# compiled.
libcpp_big_endian = "big endian" in gdb.execute("show endian",
to_string=True)
# This logical structure closely follows the original code (which is clearer
# in C++). Keep them parallel to make them easier to compare.
if libcpp_abi_alternate_string_layout:
if libcpp_big_endian:
if _libcpp_big_endian:
return short_size >> 1
else:
return short_size
elif libcpp_big_endian:
elif _libcpp_big_endian:
return short_size
else:
return short_size >> 1
@ -969,6 +965,14 @@ _libcxx_printer_name = "libcxx_pretty_printer"
# certain pathological cases. Limit our pretty printers to the progspace.
def _register_libcxx_printers(event):
progspace = event.new_objfile.progspace
# It would be ideal to get the endianness at print time, but
# gdb.execute clears gdb's internal wrap buffer, removing any values
# already generated as part of a larger data structure, and there is
# no python api to get the endianness. Mixed-endianness debugging
# rare enough that this workaround should be adequate.
_libcpp_big_endian = "big endian" in gdb.execute("show endian",
to_string=True)
if not getattr(progspace, _libcxx_printer_name, False):
print("Loading libc++ pretty-printers.")
gdb.printing.register_pretty_printer(