HLJ2009 created this revision.
HLJ2009 added a reviewer: aaron.ballman.
Herald added a subscriber: cfe-commits.
I tested the alias attribute on my own Apple laptop (Target:
x86_64-apple-darwin17.5.0). First, I use __has_attribute to test that the alias
is usable or not. The test code is as follows:
#include <stdio.h>
void print() {
#if __has_attribute(alias)
printf("has attribute");
#else
printf("has not attribute");
#endif
}
int main() {
print();
return 0;
}
Compiled using clang, the output result is has attribute, but when i use the
following code to verify
#include <stdio.h>
int oldname = 1;
extern int newname __attribute__((alias("oldname"))); // declaration
void foo(void)
{
printf("newname = %d\n", newname); // prints 1
}
int main() {
foo();
return 0;
}
It told me alias.c:3:35: error: aliases are not supported on darwin.so we
should exclude the platform.
Repository:
rC Clang
https://reviews.llvm.org/D46805
Files:
include/clang/Basic/Attr.td
utils/TableGen/ClangAttrEmitter.cpp
Index: utils/TableGen/ClangAttrEmitter.cpp
===================================================================
--- utils/TableGen/ClangAttrEmitter.cpp
+++ utils/TableGen/ClangAttrEmitter.cpp
@@ -2784,6 +2784,11 @@
GenerateTargetSpecificAttrCheck(R, Test, FnName, "OSes", "T.getOS()",
"llvm::Triple::");
+ // If the Negated is 1 in specific, it indicates that the attribute
+ // is not supported on this platform
+ if(R->getValueAsBit("Negated"))
+ Test = "!(" + Test + ")";
+
// If one or more CXX ABIs are specified, check those as well.
GenerateTargetSpecificAttrCheck(R, Test, FnName, "CXXABIs",
"Target.getCXXABI().getKind()",
Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -296,6 +296,9 @@
// Specifies Object Formats for which the target applies, based off the
// ObjectFormatType enumeration in Triple.h
list<string> ObjectFormats;
+ // It indicates that a certain attribute is not supported on a specific
+ // platform, turn on support for this attribute by default
+ bit Negated = 0;
}
class TargetArch<list<string> arches> : TargetSpec {
@@ -318,6 +321,13 @@
let ObjectFormats = ["ELF"];
}
+// We do not support the alias attribute on Apple platforms,
+// so I define a platform other than the Apple platform.
+def TargetDarwinNegative : TargetArch<["x86", "x86_64"]> {
+ let OSes = ["MacOSX"];
+ let Negated = 1;
+}
+
// Attribute subject match rules that are used for #pragma clang attribute.
//
// A instance of AttrSubjectMatcherRule represents an individual match rule.
@@ -553,7 +563,8 @@
let Documentation = [Undocumented];
}
-def Alias : Attr {
+// We do not support alias attribute on Apple platform, so we exclude the
platform.
+def Alias : Attr, TargetSpecificAttr<TargetDarwinNegative> {
let Spellings = [GCC<"alias">];
let Args = [StringArgument<"Aliasee">];
let Subjects = SubjectList<[Function, GlobalVar], ErrorDiag>;
Index: utils/TableGen/ClangAttrEmitter.cpp
===================================================================
--- utils/TableGen/ClangAttrEmitter.cpp
+++ utils/TableGen/ClangAttrEmitter.cpp
@@ -2784,6 +2784,11 @@
GenerateTargetSpecificAttrCheck(R, Test, FnName, "OSes", "T.getOS()",
"llvm::Triple::");
+ // If the Negated is 1 in specific, it indicates that the attribute
+ // is not supported on this platform
+ if(R->getValueAsBit("Negated"))
+ Test = "!(" + Test + ")";
+
// If one or more CXX ABIs are specified, check those as well.
GenerateTargetSpecificAttrCheck(R, Test, FnName, "CXXABIs",
"Target.getCXXABI().getKind()",
Index: include/clang/Basic/Attr.td
===================================================================
--- include/clang/Basic/Attr.td
+++ include/clang/Basic/Attr.td
@@ -296,6 +296,9 @@
// Specifies Object Formats for which the target applies, based off the
// ObjectFormatType enumeration in Triple.h
list<string> ObjectFormats;
+ // It indicates that a certain attribute is not supported on a specific
+ // platform, turn on support for this attribute by default
+ bit Negated = 0;
}
class TargetArch<list<string> arches> : TargetSpec {
@@ -318,6 +321,13 @@
let ObjectFormats = ["ELF"];
}
+// We do not support the alias attribute on Apple platforms,
+// so I define a platform other than the Apple platform.
+def TargetDarwinNegative : TargetArch<["x86", "x86_64"]> {
+ let OSes = ["MacOSX"];
+ let Negated = 1;
+}
+
// Attribute subject match rules that are used for #pragma clang attribute.
//
// A instance of AttrSubjectMatcherRule represents an individual match rule.
@@ -553,7 +563,8 @@
let Documentation = [Undocumented];
}
-def Alias : Attr {
+// We do not support alias attribute on Apple platform, so we exclude the platform.
+def Alias : Attr, TargetSpecificAttr<TargetDarwinNegative> {
let Spellings = [GCC<"alias">];
let Args = [StringArgument<"Aliasee">];
let Subjects = SubjectList<[Function, GlobalVar], ErrorDiag>;
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