[ELF][gcc compatibility]: support section names with special characters (e.g. "/")

[myatsina]

Summary

Adding support for section names withspecial characters in them (e.g. "/") .
GCC successfully compiles such section names.
This also fixes PR24520.

[majnemer]

lib/MC/MCParser/ELFAsmParser.cpp

233–248

GNU as's behavior seems to be the following: the section name is either exactly one quoted string OR it is anything other than a newline,tab,comma or semicolon.

[myatsina]

Adding support for additional special characters in the section name

[• rafael]

test/MC/ELF/section.s

16

Missing check for ~!@$%^&*()_-+={[}]|\\:<>

[myatsina]

Added missing check

[• rafael]

LGTM

lib/MC/MCParser/ELFAsmParser.cpp

bool ELFAsmParser::ParseSectionName(StringRef &SectionName) {
 
   if (getLexer().is(AsmToken::String)) {
     SectionName = getTok().getIdentifier();
     Lex();
     return false;
   }
 
   for (;;) {
-    unsigned CurSize;
     
     SMLoc PrevLoc = getLexer().getLoc();
-    if (getLexer().is(AsmToken::Minus)) {
-      CurSize = 1;
-      Lex(); // Consume the "-".
-    } else if (getLexer().is(AsmToken::String)) {
+    if (getLexer().is(AsmToken::Comma) ||
+      getLexer().is(AsmToken::EndOfStatement))
+      break;
+    
+    unsigned CurSize;
+    if (getLexer().is(AsmToken::String)) {
       CurSize = getTok().getIdentifier().size() + 2;
       Lex();
     } else if (getLexer().is(AsmToken::Identifier)) {
       CurSize = getTok().getIdentifier().size();
       Lex();
     } else {
-      break;
+      CurSize = getTok().getString().size();
+      Lex();
     }
-
     Size += CurSize;
     SectionName = StringRef(FirstLoc.getPointer(), Size);
 
     // Make sure the following token is adjacent.
     if (PrevLoc.getPointer() + CurSize != getTok().getLoc().getPointer())
       break;
   }
   if (Size == 0)

test/MC/ELF/section.s

 // RUN: llvm-mc -filetype=obj -triple x86_64-pc-linux-gnu %s -o - | llvm-readobj -s | FileCheck %s
 
 // Test that these names are accepted.
 
 .section  .note.GNU-stack,"",@progbits
 .section  .note.GNU-stack2,"",%progbits
 .section  .note.GNU-,"",@progbits
 .section  -.note.GNU,"","progbits"
+.section  src/stack.c,"",@progbits
+.section  ~!@$%^&*()_-+={[}]|\\:<>,"",@progbits
 
 // CHECK: Name: .note.GNU-stack
 // CHECK: Name: .note.GNU-stack2
 // CHECK: Name: .note.GNU-
 // CHECK: Name: -.note.GNU
+// CHECK: Name: src/stack.c
+// CHECK: Name: ~!@$%^&*()_-+={[}]|\\:<>
 
 // Test that the defaults are used
 
 .section  .init
 .section  .fini
 .section  .rodata
 .section  zed, ""