https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80759
--- Comment #36 from Daniel Santos <daniel.santos at pobox dot com> ---
Thank you for all of your work on this. The .cfi directives shouldn't be *too*
critical -- I've barely scratched the surface of learning DWARF and, iirc, the
last time I stepped through these stubs in gdb it still wasn't always able to
determine the call frame correctly (although I could be thinking of stepping
through the assembly code in the test program). I suppose this can be an issue
for somebody debugging Wine code at some future date, but I have no qualms with
removing it for now, and possibly redoing it later in more portable way (and
that actually provides the debugger with everything it needs).
Also, you *had* mentioned this linking problem in the past and I apologize for
loosing track of it. I have not actually done a thorough study of ABIs used in
other *nix operating systems, but my guess would be that all 64-bit platforms
that GCC supports use the SystemV ABI except for Windows (Cygwin & MinGW)?
This is a question outside of my expertise, so please let me know if the below
solution amenable.
I should also note that while this optimization isn't meant for Windows and
would likely almost never appear in code built for windows (unless somebody is
trying to link to objects/libs built on for *nix), support on Windows is
explicitly disabled due to the SEH unwind emit code not supporting
REG_CFA_EXPRESSION, which it requires. So we don't need the stubs on Windows
anyway.
diff --git a/libgcc/config.host b/libgcc/config.host
index 7711abf2704..f0f0d6c0916 100644
--- a/libgcc/config.host
+++ b/libgcc/config.host
@@ -1355,6 +1355,14 @@ esac
case ${host} in
i[34567]86-*-* | x86_64-*-*)
case ${host} in
+ *-*-cygwin* | *-*-mingw*)
+ ;;
+ *)
+ tmake_file="${tmake_file} i386/t-msabi"
+ ;;
+ esac
+
+ case ${host} in
*-musl*)
tmake_file="${tmake_file} i386/t-cpuinfo-static"
;;
@@ -1365,11 +1373,12 @@ i[34567]86-*-* | x86_64-*-*)
;;
esac
+
case ${host} in
i[34567]86-*-linux* | x86_64-*-linux* | \
i[34567]86-*-kfreebsd*-gnu | x86_64-*-kfreebsd*-gnu | \
i[34567]86-*-gnu*)
- tmake_file="${tmake_file} t-tls i386/t-linux i386/t-msabi
t-slibgcc-libgcc"
+ tmake_file="${tmake_file} t-tls i386/t-linux t-slibgcc-libgcc"
if test "$libgcc_cv_cfi" = "yes"; then
tmake_file="${tmake_file} t-stack i386/t-stack-i386"
fi
As for the stubs, I don't think there's a real need to stay tied to gas
extensions -- truth be told, this was my first actual non-inline, x86 assembly
code I have written (last time I did assembly prior was on a Motorola
6502/6510), so I'm sorry to have forced you to become my unwitting tutor! :)
This is assembly with cpp, so the gas .macro could be replaced with a cpp
macro, but is that acceptable considering that it would result in multiple
instructions on the same line delimited by semicolons instead of "\n\t"? So
should I just copy & paste the instructions and be done with it?
Thanks,
Daniel
