C preprocessor bug

[Jonathan Wakely]

On 22/07/24 12:24 +0300, Ovidiu Panait wrote:
>Hi,
>
>When processing large header files, the C preprocessor reports error 
>on the wrong line.

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>This is 100% reproducible on my side with gcc mainline.
>
>Reproducer:
>
> # Build
>mkdir build; cd build
>../configure --host=x86_64-pc-linux-gnu --target=x86_64-wrs-linux 
>--enable-languages=c --disable-multilib --disable-libstdcxx-pch 
>--disable-libsanitizer --disable-libssp --disable-libquadmath 
>--disable-libquadmath-support --disable-libgomp --disable-libvtv 
>--disable-bootstrap
>make all-host -j$(nproc)
>mkdir install; make install-host DESTDIR=$(realpath ./install) -j$(nproc)
>
>
> # Generate testcase
>mkdir testcase; cd testcase
>cat > main.c <<EOF
>extern int main_begins;
>extern int main_begins;
>extern int main_begins;
>#include "header1.h"
>EOF
>echo -n > header1.h
>for i in {1..327676}; do
>    echo "extern int header1_begins;" >> header1.h
>done
>cat >> header1.h <<EOF
>#include "header2.h"
>extern int header1 ends;
>EOF
>echo -n > header2.h
>
>
> # Test
>../install/usr/local/bin/x86_64-wrs-linux-gcc main.c
>In file included from main.c:4:
>header1.h:327677:20: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or 
>‘__attribute__’ before ‘ends’
>327677 | #include "header2.h"
>       |                    ^
>
>
>The line where the error is reported("327677") is bogus, the actual 
>error is on the next line("327678") in header1.h:
>
>$ cat -n header1.h | tail -n3
>327676    extern int header1_begins;
>327677    #include "header2.h"
>327678    extern int header1 ends;
>
>
>Ovidiu