c/10675: Compile time increases quadratically with struct size

hzoli@hzoli.2y.net hzoli@hzoli.2y.net
Thu May 8 02:20:00 GMT 2003

>Number:         10675
>Category:       c
>Synopsis:       Compile time increases quadratically with struct size
>Confidential:   no
>Severity:       critical
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Thu May 08 01:56:00 UTC 2003
>Originator:     Zoltan Hidvegi
>Release:        3.2.3 (Debian testing/unstable)
System: Linux hzoli 2.4.21-rc1-ac3 #1 Wed Apr 30 11:10:22 CDT 2003 i686 unknown unknown GNU/Linux
Architecture: i686

host: i386-pc-linux-gnu
build: i386-pc-linux-gnu
target: i386-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,objc,ada --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-include-dir=/usr/include/c++/3.2 --enable-shared --with-system-zlib --enable-nls --without-included-gettext --enable-__cxa_atexit --enable-clocale=gnu --enable-java-gc=boehm --enable-objc-gc i386-linux
The compile time increases quadratically (actually more than
quadratically) with the number of members in a struct.

The following is a shell script that will generate a struct with a
given number of members and instantiates a global variable of that

------- BEGIN biggen.sh -------------
#! /bin/sh
let i=0
echo 'struct foo {'
while [ "$i" -lt "$1" ]
    echo "int i_$((i=i+1));"
echo '};'
echo 'struct foo f;'
--------- END biggen.sh -------------

Run it like this:
./biggen.sh 10000 > big.c; cc -c big.c
Change the number from 10000 and see how the compile time is affected.
E.g. on my 1.73GHz Athlon, 5000 members take 1.66s, 10000 takes 8.5s and 20000
takes 35.91s.  Unfortunately, I need to compile a generated struct
with several hundred thousand members, which is not feasible.


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