[llvm-bugs] [Bug 28427] New: Endless stream of warnings when using GCC with -Wa, -q and Clang Integrated Assembler

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https://llvm.org/bugs/show_bug.cgi?id=28427

            Bug ID: 28427
           Summary: Endless stream of warnings when using GCC with -Wa,-q
                    and Clang Integrated Assembler
           Product: compiler-rt
           Version: 3.8
          Hardware: Macintosh
                OS: All
            Status: NEW
          Severity: normal
          Priority: P
         Component: compiler-rt
          Assignee: unassignedbugs at nondot.org
          Reporter: noloader at gmail.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

When using MacPorts GCC on OS X and enlisting the Clang Integrated Assembler
via -Wa,-q, the assembler produces a stream of warnings for each file. A simple
test case is shown below (but a real project produces thousands of them).

I found LLVM Commit r250349, Stop generating coal sections. Here's the code
responsible, but its not clear to me how to disable the warning.

+  // Issue a warning if the target is not powerpc and Section is a *coal*
section.
+  Triple TT = getParser().getContext().getObjectFileInfo()->getTargetTriple();
+  Triple::ArchType ArchTy = TT.getArch();
+
+  if (ArchTy != Triple::ppc && ArchTy != Triple::ppc64) {
+    StringRef NonCoalSection = StringSwitch<StringRef>(Section)
+                                   .Case("__textcoal_nt", "__text")
+                                   .Case("__const_coal", "__const")
+                                   .Case("__datacoal_nt", "__data")
+                                   .Default(Section);
+
+    if (!Section.equals(NonCoalSection)) {
+      StringRef SectionVal(Loc.getPointer());
+      size_t B = SectionVal.find(',') + 1, E = SectionVal.find(',', B);
+      SMLoc BLoc = SMLoc::getFromPointer(SectionVal.data() + B);
+      SMLoc ELoc = SMLoc::getFromPointer(SectionVal.data() + E);
+      getParser().Warning(Loc, "section \"" + Section + "\" is deprecated",
+                          SMRange(BLoc, ELoc));
+      getParser().Note(Loc, "change section name to \"" + NonCoalSection +
+                       "\"", SMRange(BLoc, ELoc));
+    }
+  }
+

**********

The test case depends upon -g2 and -O2. if I omit them, then the warnings are
not present.

$ cat test.cxx 
#include <iostream>
#include <algorithm>

int main(int argc, char* argv[])
{
  std::for_each(argv, argv+argc, [](char* str)
      {std::cout << str << std::endl;});

  return 0;
}

$ /opt/local/bin/g++-mp-6 -march=native -g2 -O2 -std=c++11 -Wa,-q test.cxx -o
test.exe
/var/folders/mk/y7lk0xrx72lcn_2q3d12jcch0000gn/T//cc1dR6yG.s:3:11: warning:
section "__textcoal_nt" is deprecated
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~
/var/folders/mk/y7lk0xrx72lcn_2q3d12jcch0000gn/T//cc1dR6yG.s:3:11: note: change
section name to "__text"
        .section __TEXT,__textcoal_nt,coalesced,pure_instructions
                 ^      ~~~~~~~~~~~~~

**********

When the MacPorts GCC compiler encounters -Wa,-q, it uses /opt/local/bin/clang
as the assembler rather than /opt/local/bin/as. Here are the relevant versions.

$ /opt/local/bin/g++-mp-6 --version
g++-mp-6 (MacPorts gcc6 6.1.0_0) 6.1.0
Copyright (C) 2016 Free Software Foundation, Inc.

$ /opt/local/bin/clang --version
clang version 3.8.0 (branches/release_38 262722)
Target: x86_64-apple-darwin12.6.0

$ /opt/local/bin/as -version
Apple Inc version cctools-877.8, GNU assembler version 1.38

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