Hi Ilya,
On Wed, 2023-02-08 at 13:22 +0100, Ilya Leoshkevich wrote:
> If I build:
>
> const char *const apba__ __asm ("argp_program_bug_address") \
> __attribute__ ((used)) = "foobarbaz";
>
> with C and C++, the difference is going to be:
>
> @@ -1,6 +1,5 @@
> .file "1.c"
> .text
> - .globl argp_program_bug_address
> .section .rodata.str1.1,"aMS",@progbits,1
> .LC0:
> .string "foobarbaz"
>
> This must have to do with C and C++ standards treating const
> differently [1]. The solution is to add extern:
>
> --- a/lib/printversion.h
> +++ b/lib/printversion.h
> @@ -44,6 +44,7 @@ void print_version (FILE *stream, struct argp_state
> *state);
> void (*const apvh) (FILE *, struct argp_state *) \
> __asm ("argp_program_version_hook")
> #define ARGP_PROGRAM_BUG_ADDRESS_DEF \
> + extern const char *const apba__; \
> const char *const apba__ __asm ("argp_program_bug_address") \
> __attribute__ ((used))
>
> I can include this in v2 if it works for you.
>
> [1]
> https://stackoverflow.com/questions/8908071/const-correctness-in-c-vs-c
O nice, that explains it. But then in that case I don't think you need
the __attribute__ ((used)) anymore.
Also as a nitpick the multiline define could be just a single line if
you declare the extern on its own in printversion.h.
And it would be nice to also cleanup apvh/argp_program_version_hook so
it too works with c++, so we can remove the hack in debuginfod.cxx.
Does the following work for you?
diff --git a/lib/printversion.h b/lib/printversion.h
index a9e059ff..bc9ca7ae 100644
--- a/lib/printversion.h
+++ b/lib/printversion.h
@@ -40,9 +40,11 @@ void print_version (FILE *stream, struct argp_state *state);
variables as non-const (which is correct in general). But we can
do better, it is not going to change. So we want to move them into
the .rodata section. Define macros to do the trick. */
+extern void (*const apvh) (FILE *, struct argp_state *);
#define ARGP_PROGRAM_VERSION_HOOK_DEF \
void (*const apvh) (FILE *, struct argp_state *) \
__asm ("argp_program_version_hook")
+extern const char *const apba__;
#define ARGP_PROGRAM_BUG_ADDRESS_DEF \
const char *const apba__ __asm ("argp_program_bug_address")
diff --git a/debuginfod/debuginfod.cxx b/debuginfod/debuginfod.cxx
index 4271acf4..99b1f2b9 100644
--- a/debuginfod/debuginfod.cxx
+++ b/debuginfod/debuginfod.cxx
@@ -348,7 +348,7 @@ static const char DEBUGINFOD_SQLITE_CLEANUP_DDL[] =
/* Name and version of program. */
-/* ARGP_PROGRAM_VERSION_HOOK_DEF = print_version; */ // not this simple for C++
+ARGP_PROGRAM_VERSION_HOOK_DEF = print_version;
/* Bug report address. */
ARGP_PROGRAM_BUG_ADDRESS_DEF = PACKAGE_BUGREPORT;
@@ -4171,7 +4171,6 @@ main (int argc, char *argv[])
/* Parse and process arguments. */
int remaining;
- argp_program_version_hook = print_version; // this works
(void) argp_parse (&argp, argc, argv, ARGP_IN_ORDER, &remaining, NULL);
if (remaining != argc)
error (EXIT_FAILURE, 0,
Thanks,
Mark
