The following compiler warning is emitted for the BACKTRACE_X86STACK
part of lib/isc/backtrace.c:
backtrace.c: In function ‘getrbp’:
backtrace.c:142:1: warning: no return statement in function returning non-void [-Wreturn-type]
While getrbp() stores the value of the RBP register in the RAX register
and thus does attempt to return a value, this is not enough for an
optimizing compiler to always produce the expected result. With -O2,
the following machine code may be generated in isc_backtrace_gettrace():
0x00007ffff7b0ff7a <+10>: mov %rbp,%rax
0x00007ffff7b0ff7d <+13>: mov $0x17,%eax
0x00007ffff7b0ff82 <+18>: retq
The above is equivalent to:
sp = (void **)getrbp();
return (ISC_R_NOTFOUND);
and results in the backtrace never getting printed.
Fix by using an intermediate variable. With this change in place, the
machine code generated with -O2 becomes something like:
0x00007ffff7af5638 <+24>: mov $0x17,%eax
0x00007ffff7af563d <+29>: mov %rbp,%rdx
0x00007ffff7af5640 <+32>: test %rdx,%rdx
0x00007ffff7af5643 <+35>: je 0x7ffff7af56bd <isc_backtrace_gettrace+157>
...
0x00007ffff7af56bd <+157>: retq
(Note that this method of grabbing a stack trace is finicky anyway
because in order for RBP to be relied upon, -fno-omit-stack-frame must
be present among CFLAGS.)
Some operating systems (e.g. Linux, FreeBSD) provide the
_Unwind_Backtrace() function in libgcc_s.so, which is automatically
linked into any binary using the functions provided by that library. On
OpenBSD, though, _Unwind_Backtrace() is provided by libc++abi.so, which
is not automatically linked into binaries produced by the stock system C
compiler.
Meanwhile, lib/isc/backtrace.c assumes that any GNU-compatible toolchain
allows _Unwind_Backtrace() to be used without any extra provisions in
the build system. This causes build failures on OpenBSD (and possibly
other systems).
Instead of making assumptions, actually check for _Unwind_Backtrace()
support in the toolchain if the backtrace() function is unavailable.
Start enforcing the clang-format rules on changed files
Closes#46
See merge request isc-projects/bind9!3063
(cherry picked from commit a04cdde45d)
d2b5853b Start enforcing the clang-format rules on changed files
618947c6 Switch AlwaysBreakAfterReturnType from TopLevelDefinitions to All
654927c8 Add separate .clang-format files for headers
5777c44a Reformat using the new rules
60d29f69 Don't enforce copyrights on .clang-format
adjust clang-format options to get closer to ISC style
See merge request isc-projects/bind9!3061
(cherry picked from commit d3b49b6675)
0255a974 revise .clang-format and add a C formatting script in util
e851ed0b apply the modified style
Add curly braces using uncrustify and then reformat with clang-format back
Closes#46
See merge request isc-projects/bind9!3057
(cherry picked from commit 67b68e06ad)
36c6105e Use coccinelle to add braces to nested single line statement
d14bb713 Add copy of run-clang-tidy that can fixup the filepaths
056e133c Use clang-tidy to add curly braces around one-line statements
Reformat source code with clang-format
Closes#46
See merge request isc-projects/bind9!2156
(cherry picked from commit 7099e79a9b)
4c3b063e Import Linux kernel .clang-format with small modifications
f50b1e06 Use clang-format to reformat the source files
11341c76 Update the definition files for Windows
df6c1f76 Remove tkey_test (which is no-op anyway)
