[NFCI][lldb][test] Avoid GNU extension for specifying mangling

[tambry]

asm() on function declarations is used for specifying the mangling. But that specific spelling is a GNU extension unlike __asm().

Found by building with -std=c2y in Clang's C frontend's config file.

[llvmbot]

@llvm/pr-subscribers-lldb

Author: Raul Tambre (tambry)

Changes

asm() on function declarations is used for specifying the mangling. But that specific spelling is a GNU extension unlike __asm().

Found by building with -std=c2y in Clang's C frontend's config file.

---

Full diff: https://github.com/llvm/llvm-project/pull/167221.diff

1 Files Affected:

• (modified) lldb/test/Shell/Unwind/Inputs/call-asm.c (+2-2)

diff --git a/lldb/test/Shell/Unwind/Inputs/call-asm.c b/lldb/test/Shell/Unwind/Inputs/call-asm.c
index b154c1ac1385d..778c16b36a761 100644
--- a/lldb/test/Shell/Unwind/Inputs/call-asm.c
+++ b/lldb/test/Shell/Unwind/Inputs/call-asm.c
@@ -1,3 +1,3 @@
-int asm_main() asm("asm_main");
-
+// Explicit mangling is necessary as on Darwin an underscore is prepended to the symbol.
+int asm_main() __asm("asm_main");
 int main() { return asm_main(); }

[Michael137]

What's the specific error/warning you're getting? This seems like a perfectly supported Clang attribute: https://clang.llvm.org/docs/AttributeReference.html#asm

and the spelling you're changing it to is not listed in "Supported Syntaxes".

[tambry]

@Michael137 The error:

Exit Code: 1

Command Output (stdout):
--
# RUN: at line 7
/home/tambre/dev/llvm/build/bin/clang --target=specify-a-target-or-use-a-_host-substitution --target=x86_64-pc-linux-gnu -pthread -fmodules-cache-path=/home/tambre/dev/llvm/build/lldb-test-build.noindex/module-cache-clang/lldb-shell /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/call-asm.c -x assembler-with-cpp /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/thread-step-out-ret-addr-check.s -o /home/tambre/dev/llvm/build/tools/lldb/test/Shell/Unwind/Output/thread-step-out-ret-addr-check.test.tmp
# executed command: /home/tambre/dev/llvm/build/bin/clang --target=specify-a-target-or-use-a-_host-substitution --target=x86_64-pc-linux-gnu -pthread -fmodules-cache-path=/home/tambre/dev/llvm/build/lldb-test-build.noindex/module-cache-clang/lldb-shell /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/call-asm.c -x assembler-with-cpp /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/thread-step-out-ret-addr-check.s -o /home/tambre/dev/llvm/build/tools/lldb/test/Shell/Unwind/Output/thread-step-out-ret-addr-check.test.tmp
# .---command stderr------------
# | clang: warning: argument unused during compilation: '-fmodules-cache-path=/home/tambre/dev/llvm/build/lldb-test-build.noindex/module-cache-clang/lldb-shell' [-Wunused-command-line-argument]
# | /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/call-asm.c:2:16: error: expected function body after function declarator
# |     2 | int asm_main() asm("asm_main");
# |       |                ^
# | /home/tambre/dev/llvm/lldb/test/Shell/Unwind/Inputs/call-asm.c:3:21: error: use of undeclared identifier 'asm_main'
# |     3 | int main() { return asm_main(); }
# |       |                     ^~~~~~~~
# | 2 errors generated.
# `-----------------------------
# error: command failed with exit status: 1

The asm() syntax is C++/GNU-only (or with -fgnu-keywords). I'll add the __asm syntax to documentation (#167226).
No strong from my side between __asm and __asm__ as both work the same (unlike asm being GNU-only).