Trouble building gcc 4.6: undefined reference to `yylex'

Question

I'm trying to build gcc 4.6, but I'm getting some linker errors that look like it means bison or flex isn't getting linked to. When the makefile issues this command:

gcc   -g -fkeep-inline-functions -DIN_GCC   -W -Wall -Wwrite-strings -Wcast-qual -Wstrict-prototypes -Wmissing-prototypes -Wmissing-format-attribute -pedantic -Wno-long-long -Wno-variadic-macros -Wno-overlength-strings -Wold-style-definition -Wc++-compat -fno-common  -DHAVE_CONFIG_H -DGENERATOR_FILE  -o build/gengtype \
        build/gengtype.o build/errors.o build/gengtype-lex.o build/gengtype-parse.o build/version.o ../../build-x86_64-unknown-linux-gnu/libiberty/libiberty.a

It tells me:

/home/chris/code/gcc/trunk/host-x86_64-unknown-linux-gnu/gcc/../.././gcc/gengtype.c:960: undefined reference to `lexer_line'
... undefined reference to `yylex'
... undefined reference to `yybegin'
... undefined reference to `yyend'

I've installed Flex and Bison, and even tried several Bison variants with the same result. Does anybody know what else this might mean?

Which versions of flex, bison and other tools have you used? Was the same error occurring at every such attempt? Some old discussions that Google finds for _gengtype.c undefined reference to `lexer_line' ... undefined reference to `yylex'_ points to a possible problem with flex. Are you building from the svn trunk? Or from some distribution's source repository? — vpit3833, Nov 24 '10 at 06:16
The same happened to me. Is this some kind of bug that first itme installation will not work properly? — Aman Deep Gautam, Jun 30 '12 at 01:42

score 49 · Accepted Answer · edited Dec 18 '13 at 15:27

49

Same happened to me, it was due to lack of flex and bison. After installing flex and bison, I ran make distclean and ./configure, then it compiled fine.

edited Dec 18 '13 at 15:27

Ross Rogers

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answered Jan 29 '11 at 19:01

Ricbit

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Aha, make *distclean*. I'd tried just a `make clean`, but that didn't work. I was about to try nuking from orbit like @Chris suggested, but this worked just as well. – Adam Rosenfield Mar 18 '11 at 15:09
For the record this was the fix for a standard Ubuntu install (11.04) – Hooked Aug 30 '11 at 14:27
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The gcc installation docs recommend not running configure in the source dir. If you run ../gcc-srcdir/configure from a different dir then the source dir remains untouched and you can just remove the whole obj dir. That is more reliable (and faster) than "make distclean" – Jonathan Wakely Dec 08 '13 at 14:54
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Why does configure not warn about the lack of flex? It [was so picky with GMP!](http://stackoverflow.com/questions/9253695/building-gcc-requires-gmp-4-2-mpfr-2-3-1-and-mpc-0-8-0) – Ciro Santilli Путлер Капут 六四事 May 13 '15 at 10:12

score 3 · Answer 2 · answered Dec 31 '12 at 17:00

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Ran into this as well but the fix for me was to install bisonc++, for whatever reason I only had bison installed.

answered Dec 31 '12 at 17:00

Justin Buser

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I don't understand why this was down voted, this helped me out trying to compile a gcc 6 snapshot. – Luke Antins May 12 '15 at 03:12

score 1 · Answer 3 · answered Nov 24 '10 at 08:21

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It just got into some weird state since I did ./configure and tried to build it before having bison and flex set up properly. Calling make clean wasn't enough. I wiped out the whole thing and did a fresh checkout and it builds fine now.

answered Nov 24 '10 at 08:21

Chris

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Trouble building gcc 4.6: undefined reference to `yylex'

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