http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56825
Bug #: 56825
Summary: Preprocessor does not expand macro correctly if it is
an argument and argument of a macro contains ##
Classification: Unclassified
Product: gcc
Version: 4.7.2
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: preprocessor
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: ste...@gmail.com
Created attachment 29786
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29786
Test file
Ok. That is a little bit hard to explain. Consider the following macros:
#define E3N(n, ar...) E3NI(_, ##ar, n, n, n)
#define E3NI(a0, a1, a2, a3, ...) a1, a2, a3
#define USE_E3_ARG_R(n, ar...) (E3N(n, ar))
#define USE_E3_ARG_W(n, ar...) (E3N(n, ##ar))
If we write something like:
USE_E3_ARG_W(3, 4);
It expands correctly to:
(4, 3, 3);
But if we use more complicate:
USE_E3_ARG_R(5, USE_E3_ARG_R(6, 7));
It expands to:
(USE_E3_ARG_W(9, 0), 8, 8);
While I would expect:
((0, 9, 9), 8, 8);
Mind that the following expands correctly:
USE_E3_ARG_R(5, USE_E3_ARG_R(6, 7));
To:
((7, 6, 6), 5, 5);
The problem is probably related to the following paragraph in standart:
"... After the arguments for the invocation of a function-like macro have been
identified, argument substitution takes place. A parameter in the replacement
list, unless preceded by a # or ## preprocessing token or followed by a ##
preprocessing token (see below), is replaced by the corresponding argument
after all macros contained therein have been expanded..."
But IMHO this statement is relevant to the macro itself and should not apply to
the argument of the macro containing ## to remove comma (##ar in our case).
I know that it will not make any point but Eclipse expands all these macros
correctly with internal macro expansion.
Output of the test compilation:
gcc-mp-4.7 test2.c -v --save-temps
Using built-in specs.
COLLECT_GCC=gcc-mp-4.7
COLLECT_LTO_WRAPPER=/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/lto-wrapper
Target: x86_64-apple-darwin12
Configured with: ../gcc-4.7.2/configure --prefix=/opt/local
--build=x86_64-apple-darwin12
--enable-languages=c,c++,objc,obj-c++,lto,fortran,java
--libdir=/opt/local/lib/gcc47 --includedir=/opt/local/include/gcc47
--infodir=/opt/local/share/info --mandir=/opt/local/share/man
--datarootdir=/opt/local/share/gcc-4.7 --with-libiconv-prefix=/opt/local
--with-local-prefix=/opt/local --with-system-zlib --disable-nls
--program-suffix=-mp-4.7 --with-gxx-include-dir=/opt/local/include/gcc47/c++/
--with-gmp=/opt/local --with-mpfr=/opt/local --with-mpc=/opt/local
--with-ppl=/opt/local --with-cloog=/opt/local --enable-cloog-backend=isl
--disable-cloog-version-check --enable-stage1-checking --disable-multilib
--enable-lto --enable-libstdcxx-time --with-as=/opt/local/bin/as
--with-ld=/opt/local/bin/ld --with-ar=/opt/local/bin/ar
--with-bugurl=https://trac.macports.org/newticket --disable-ppl-version-check
--with-pkgversion='MacPorts gcc47 4.7.2_2'
Thread model: posix
gcc version 4.7.2 (MacPorts gcc47 4.7.2_2)
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.8.3' '-v' '-save-temps'
'-mtune=core2'
/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/cc1 -E -quiet -v
-D__DYNAMIC__ test2.c -fPIC -mmacosx-version-min=10.8.3 -mtune=core2
-fpch-preprocess -o test2.i
ignoring nonexistent directory
"/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/../../../../../x86_64-apple-darwin12/include"
#include "..." search starts here:
#include <...> search starts here:
/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/include
/opt/local/include
/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/include-fixed
/usr/include
/System/Library/Frameworks
/Library/Frameworks
End of search list.
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.8.3' '-v' '-save-temps'
'-mtune=core2'
/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/cc1 -fpreprocessed test2.i
-fPIC -quiet -dumpbase test2.c -mmacosx-version-min=10.8.3 -mtune=core2
-auxbase test2 -version -o test2.s
GNU C (MacPorts gcc47 4.7.2_2) version 4.7.2 (x86_64-apple-darwin12)
compiled by GNU C version 4.7.2, GMP version 5.0.5, MPFR version 3.1.1-p2,
MPC version 1.0.1
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
GNU C (MacPorts gcc47 4.7.2_2) version 4.7.2 (x86_64-apple-darwin12)
compiled by GNU C version 4.7.2, GMP version 5.0.5, MPFR version 3.1.1-p2,
MPC version 1.0.1
GGC heuristics: --param ggc-min-expand=100 --param ggc-min-heapsize=131072
Compiler executable checksum: 7de89c8f14784e88078e79248a999e9e
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.8.3' '-v' '-save-temps'
'-mtune=core2'
/opt/local/bin/as -v -arch x86_64 -force_cpusubtype_ALL -o test2.o test2.s
Apple Inc version cctools-836, GNU assembler version 1.38
COMPILER_PATH=/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/:/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/:/opt/local/libexec/gcc/x86_64-apple-darwin12/:/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/:/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/
LIBRARY_PATH=/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/:/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/../../../:/usr/lib/
COLLECT_GCC_OPTIONS='-mmacosx-version-min=10.8.3' '-v' '-save-temps'
'-mtune=core2'
/opt/local/libexec/gcc/x86_64-apple-darwin12/4.7.2/collect2 -dynamic -arch
x86_64 -macosx_version_min 10.8.3 -weak_reference_mismatches non-weak -o a.out
-L/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2
-L/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/../../.. test2.o
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
collect2 version 4.7.2
/opt/local/bin/ld -dynamic -arch x86_64 -macosx_version_min 10.8.3
-weak_reference_mismatches non-weak -o a.out
-L/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2
-L/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2/../../.. test2.o
-no_compact_unwind -lSystem -lgcc_ext.10.5 -lgcc -lSystem -v
@(#)PROGRAM:ld PROJECT:ld64-134.9
configured to support archs: i386 x86_64
Library search paths:
/opt/local/lib/gcc47/gcc/x86_64-apple-darwin12/4.7.2
/opt/local/lib/gcc47
/usr/lib
/usr/local/lib
Framework search paths:
/Library/Frameworks/
/System/Library/Frameworks/
Undefined symbols for architecture x86_64:
"_USE_E3_ARG_W", referenced from:
_main in test2.o
ld: symbol(s) not found for architecture x86_64
collect2: error: ld returned 1 exit status
Thanks,
Evgeny
