caio/clang-p2996
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

[llvm-cxxfilt][macOS] Don't strip underscores on macOS by default (#106233)

Browse Source 
Currently, `llvm-cxxfilt` will strip the leading underscore of its input
on macOS. Historically MachO symbols were prefixed with an extra
underscore and this is why this default exists. However, nowadays, the
`ItaniumDemangler` supports all of the following mangling prefixes:
`_Z`, `__Z`, `___Z`, `____Z`. So really `llvm-cxxfilt` can simply
forward the mangled name to the demangler and let the library decide
whether it's a valid encoding.

Compiling C++ on macOS nowadays will generate symbols with `_Z` and
`___Z` prefixes. So users trying to demangle these symbols will have to
know that they need to add the `-n` prefix. This routinely catches
people off-guard.

This patch removes the `-n` default for macOS and allows calling into
the `ItaniumDemangler` with all the `_Z` prefixes that the demangler
supports (1-4 underscores).

rdar://132714940
This commit is contained in:
Michael Buch
2024-08-28 08:14:41 +01:00
committed by GitHub
parent 3dbb6befa8
commit 0b554dd9b1
6 changed files with 22 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

5
llvm/lib/Demangle/Demangle.cpp
View File

@@ -38,8 +38,9 @@ std::string llvm::demangle(std::string_view MangledName) {
}
static bool isItaniumEncoding(std::string_view S) {
// Itanium encoding requires 1 or 3 leading underscores, followed by 'Z'.
return starts_with(S, "_Z") || starts_with(S, "___Z");
// Itanium demangler supports prefixes with 1-4 underscores.
const size_t Pos = S.find_first_not_of('_');
return Pos > 0 && Pos <= 4 && S[Pos] == 'Z';
}
static bool isRustEncoding(std::string_view S) { return starts_with(S, "_R"); }

6
llvm/test/tools/llvm-cxxfilt/invalid.test
View File

@@ -1,6 +1,8 @@
RUN: llvm-cxxfilt -n _Z1fi __Z1fi f ___ZSt1ff_block_invoke | FileCheck %s
RUN: llvm-cxxfilt -n _Z1fi __Z1fi _____Z1fi f ___ZSt1ff_block_invoke ____ZSt1ff_block_invoke | FileCheck %s
CHECK: f(int)
CHECK-NEXT: __Z1fi
CHECK-NEXT: f(int)
CHECK-NEXT: _____Z1fi
CHECK-NEXT: f
CHECK-NEXT: invocation function for block in std::f(float)
CHECK-NEXT: invocation function for block in std::f(float)

7
llvm/test/tools/llvm-cxxfilt/strip-underscore-default-darwin.test
View File

@@ -1,7 +0,0 @@
REQUIRES: system-darwin
## Show that on darwin, the default is to strip the leading underscore.
RUN: llvm-cxxfilt __Z1fv _Z2bav | FileCheck %s
CHECK: f()
CHECK: _Z2bav

8
llvm/test/tools/llvm-cxxfilt/strip-underscore-default.test
View File

@@ -1,8 +0,0 @@
UNSUPPORTED: system-darwin
## Show that on non-darwin systems, the default is to strip the leading
## underscore.
RUN: llvm-cxxfilt __Z1fv _Z2bav | FileCheck %s
CHECK: __Z1fv
CHECK: ba()

20
llvm/test/tools/llvm-cxxfilt/strip-underscore.test
View File

@@ -1,17 +1,23 @@
## Show the behaviour of --[no-]strip-underscore. This test does not test
## the platform-specific default behaviour. This is tested elsewhere.
## Show the behaviour of --[no-]strip-underscore.
RUN: llvm-cxxfilt -_ __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
RUN: llvm-cxxfilt --strip-underscore __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
RUN: llvm-cxxfilt -n __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
RUN: llvm-cxxfilt --no-strip-underscore __ZN2ns1fE _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
RUN: llvm-cxxfilt -_ ___ZN2ns1fE _____Z1fi_block_invoke _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
RUN: llvm-cxxfilt --strip-underscore __ZN2ns1fE _____Z1fi_block_invoke _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-STRIPPED
RUN: llvm-cxxfilt -n ___ZN2ns1fE _____Z1fi_block_invoke _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
RUN: llvm-cxxfilt --no-strip-underscore ___ZN2ns1fE _____Z1fi_block_invoke _ZSt1f _f _._Z3f.0v | FileCheck %s -check-prefix CHECK-UNSTRIPPED
RUN: llvm-cxxfilt -n -_ _ZSt1f | FileCheck %s -check-prefix OVERRIDE-STRIPPED
RUN: llvm-cxxfilt -_ -n _ZSt1f | FileCheck %s -check-prefix OVERRIDE-UNSTRIPPED
CHECK-STRIPPED: ns::f
CHECK-STRIPPED: invocation function for block in f(int)
CHECK-STRIPPED: _ZSt1f
CHECK-STRIPPED: _f
CHECK-STRIPPED: ._Z3f.0v
CHECK-UNSTRIPPED: __ZN2ns1fE
CHECK-UNSTRIPPED: ___ZN2ns1fE
CHECK-UNSTRIPPED: _____Z1fi_block_invoke
CHECK-UNSTRIPPED: std::f
CHECK-UNSTRIPPED: _f
CHECK-UNSTRIPPED: _._Z3f.0v
OVERRIDE-STRIPPED: _ZSt1f
OVERRIDE-UNSTRIPPED: std::f

9
llvm/tools/llvm-cxxfilt/llvm-cxxfilt.cpp
View File

@@ -165,13 +165,8 @@ int llvm_cxxfilt_main(int argc, char **argv, const llvm::ToolContext &) {
return 0;
}
// The default value depends on the default triple. Mach-O has symbols
// prefixed with "_", so strip by default.
if (opt::Arg *A =
Args.getLastArg(OPT_strip_underscore, OPT_no_strip_underscore))
StripUnderscore = A->getOption().matches(OPT_strip_underscore);
else
StripUnderscore = Triple(sys::getProcessTriple()).isOSBinFormatMachO();
StripUnderscore =
Args.hasFlag(OPT_strip_underscore, OPT_no_strip_underscore, false);
ParseParams = !Args.hasArg(OPT_no_params);