[llvm-bugs] [Bug 25506] New: macro string concatenation does not generate the expected result in an assembly macro

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https://llvm.org/bugs/show_bug.cgi?id=25506

            Bug ID: 25506
           Summary: macro string concatenation does not generate the
                    expected result in an assembly macro
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: -New Bugs
          Assignee: unassignedclangbugs at nondot.org
          Reporter: olivier at labapart.com
                CC: llvm-bugs at lists.llvm.org
    Classification: Unclassified

When the macro '#define CONCAT(a, b)  CONCAT2(a, b)' is declared, Clang inserts
the space between ',' and 'b' in the result when this macro is used in an
assembly macro definition (ie: '.macro').
For instance the call CONCAT(a, b) in an assembly macro would generate the
string 'a b' instead of 'ab'.

This use case is actually present in newlib source code
(https://sourceware.org/newlib/). GCC produces the expected result.

If I replace '#define CONCAT(a, b)  CONCAT2(a, b)' by '#define CONCAT(a, b) 
CONCAT2(a,b)' then the expected result is generated.

Here is the example:

----- hello.S -----
/* ANSI concatenation macros.  */
#define CONCAT(a, b)  CONCAT2(a, b)
#define CONCAT2(a, b) a##b

#ifndef __USER_LABEL_PREFIX__
#error  __USER_LABEL_PREFIX__ not defined
#endif

#define SYM(x) CONCAT (__USER_LABEL_PREFIX__, x)

        .text
        .align
        bl      SYM(setjmp)

.macro FUNC_START name
        .text
        .align 2
        .globl SYM (\name)
SYM (\name):
.endm

        FUNC_START setjmp
        bx lr
----------------------

$ clang-3.8 -target arm-none-eabi -c hello.S
<instantiation>:3:18: error: unexpected token in directive
        .globl _ setjmp
                 ^
hello.S:22:2: note: while in macro instantiation
 FUNC_START setjmp
 ^
<instantiation>:4:9: error: unexpected token in argument list
_ setjmp:
        ^
hello.S:22:2: note: while in macro instantiation
 FUNC_START setjmp
 ^

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