Hi all,
the following works for me. I have only tried a normal build (where it
does silence the same warning) and not an LTO build and I just believed
the comment - see attached patch. Comments?
On 28.09.23 08:25, Richard Biener via Fortran wrote:
This particular place in libgfortran has
/* write_z, which calls xtoa_big, is called from transfer.c,
formatted_transfer_scalar_write. There it is passed the kind as
argument, which means a maximum of 16. The buffer is large
enough, but the compiler does not know that, so shut up the
warning here. */
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wstringop-overflow"
*q = '\0';
#pragma GCC diagnostic pop
so obviously the #pragma doesn't survive through LTO. Somehow I think
this is a known bug, but maybe I misremember (I think we are not streaming
any of the ad-hoc location parts).
I have replaced it now by the assert that "len <= 16", i.e.
+ if (len > 16)
+ __builtin_unreachable ();
Build + tested on x86-64-gnu-linux
Comment? OK for mainline?
Tobias
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libgfortran: Use __builtin_unreachable() not -Wno-stringop-overflow to silence warning
libgfortran/
* io/write.c (xtoa_big): Change a 'GCC diagnostic ignored
"-Wstringop-overflow"' to an assumption (via __builtin_unreachable).
libgfortran/io/write.c | 17 +++++++++--------
1 file changed, 9 insertions(+), 8 deletions(-)
diff --git a/libgfortran/io/write.c b/libgfortran/io/write.c
index 5d47a6d25f7..00c8fd2e288 100644
--- a/libgfortran/io/write.c
+++ b/libgfortran/io/write.c
@@ -1179,6 +1179,15 @@ xtoa_big (const char *s, char *buffer, int len, GFC_UINTEGER_LARGEST *n)
uint8_t h, l;
int i;
+ /* write_z, which calls xtoa_big, is called from transfer.c,
+ formatted_transfer_scalar_write. There it is passed the kind as
+ 'len' argument, which means a maximum of 16. The buffer is large
+ enough, but the compiler does not know that, so shut up the
+ warning here. */
+
+ if (len > 16)
+ __builtin_unreachable ();
+
q = buffer;
if (__BYTE_ORDER__ == __ORDER_BIG_ENDIAN__)
@@ -1212,15 +1221,7 @@ xtoa_big (const char *s, char *buffer, int len, GFC_UINTEGER_LARGEST *n)
}
}
- /* write_z, which calls xtoa_big, is called from transfer.c,
- formatted_transfer_scalar_write. There it is passed the kind as
- argument, which means a maximum of 16. The buffer is large
- enough, but the compiler does not know that, so shut up the
- warning here. */
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wstringop-overflow"
*q = '\0';
-#pragma GCC diagnostic pop
if (*n == 0)
return "0";
