bug: cpp(1) token pasting failure

bug: cpp(1) token pasting failure

[Nick Owens]

[-- Attachment #1: Type: text/plain, Size: 1100 bytes --]

the attached C program will fail to be preprocessed by cpp(1) with the
following output. for comparison, the gcc -E test.c output follows as
well. this specific example was extracted from tinycc.

9front cpp(1):
term% cpp concat.c
cpp: concat.c:8 Bad token jo) produced by ##
cpp: concat.c:8 No newline at end of file
cpp: concat.c:8 EOF in macro arglist
cpp: concat.c:8 Disagreement in number of macro arguments
#line 1 "/usr/glenda/code/c/trash/concat.c"


#line 4 "/usr/glenda/code/c/trash/concat.c"

enum token {
        TOK_NULL

 DEF_ASM(jo #undef DEF};static const char keywords[] = #define DEF(id,
str) str "\0" DEF_ASMTEST(j,)#undef DEF;int main(int argc, char
*argv[]){        return -1;}#line 23
"/usr/glenda/code/c/trash/concat.c"

gcc -E:
mischief@omicron:/tmp $ gcc -E concat.c
# 1 "concat.c"
# 1 "<built-in>"
# 1 "<command-line>"
# 31 "<command-line>"
# 1 "/usr/include/stdc-predef.h" 1 3 4
# 32 "<command-line>" 2
# 1 "concat.c"




enum token {
        TOK_NULL

,TOK_ASM_jo

};

static const char keywords[] =

"jo" "\0"

;



int
main(int argc, char *argv[])
{
        return 0;
}

[-- Attachment #2: concat.c --]
[-- Type: text/x-csrc, Size: 356 bytes --]

#define DEF_ASM(x) DEF(TOK_ASM_ ## x, #x)
#define DEF_ASMTEST(x,suffix) \
 DEF_ASM(x ## o ## suffix)

enum token {
        TOK_NULL
#define DEF(id, str) ,id
DEF_ASMTEST(j,)
#undef DEF
};

static const char keywords[] =
#define DEF(id, str) str "\0"
DEF_ASMTEST(j,)
#undef DEF
;

#define DEF(id, str)

int
main(int argc, char *argv[])
{
        return 0;
}

Re: [9front] bug: cpp(1) token pasting failure

[Ethan Gardener]

On Sun, Sep 16, 2018, at 9:54 PM, Nick Owens wrote:
>  DEF_ASM(jo #undef DEF};static const char keywords[] = #define DEF(id,
> str) str "\0" DEF_ASMTEST(j,)#undef DEF;int main(int argc, char
> *argv[]){        return -1;}#line 23

i thought you could only use preprocessor directives at the start of a line.  i'm pretty sure i learned that particular point, but it was probably in the 90s.

Re: [9front] bug: cpp(1) token pasting failure

[Nick Owens]

i believe macros can appear anywhere, but that particular output is
the result of cpp(1)'s token pasting failure - it is not the correct
output.
On Mon, Sep 17, 2018 at 3:17 AM Ethan Gardener <eekee57@fastmail.fm> wrote:
>
> On Sun, Sep 16, 2018, at 9:54 PM, Nick Owens wrote:
> >  DEF_ASM(jo #undef DEF};static const char keywords[] = #define DEF(id,
> > str) str "\0" DEF_ASMTEST(j,)#undef DEF;int main(int argc, char
> > *argv[]){        return -1;}#line 23
>
> i thought you could only use preprocessor directives at the start of a line.  i'm pretty sure i learned that particular point, but it was probably in the 90s.