On 3/3/20 11:50 AM, Paul Menzel wrote:
Date: Tue, 3 Mar 2020 16:24:46 +0100
GCC 10 gives the warnings below:
In file included from out/ccode32flat.o.tmp.c:54:
./src/tcgbios.c: In function 'tpm20_write_EfiSpecIdEventStruct':
./src/tcgbios.c:290:30: warning: array subscript '(<unknown>) +
4294967295' is outside the bounds of an interior zero-length array 'struct
TCG_EfiSpecIdEventAlgorithmSize[0]' [-Wzero-length-bounds]
290 | event.hdr.digestSizes[count].algorithmId =
be16_to_cpu(sel->hashAlg);
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~
In file included from ./src/tcgbios.c:22,
from out/ccode32flat.o.tmp.c:54:
./src/std/tcg.h:527:7: note: while referencing 'digestSizes'
527 | } digestSizes[0];
| ^~~~~~~~~~~
In file included from out/ccode32flat.o.tmp.c:54:
./src/tcgbios.c:291:30: warning: array subscript '(<unknown>) +
4294967295' is outside the bounds of an interior zero-length array 'struct
TCG_EfiSpecIdEventAlgorithmSize[0]' [-Wzero-length-bounds]
291 | event.hdr.digestSizes[count].digestSize = hsize;
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~
In file included from ./src/tcgbios.c:22,
from out/ccode32flat.o.tmp.c:54:
./src/std/tcg.h:527:7: note: while referencing 'digestSizes'
527 | } digestSizes[0];
| ^~~~~~~~~~~
[Description copied from Gustavo A. R. Silva <gust...@embeddedor.com>
from his Linux kernel commits.]
The current codebase makes use of the zero-length array language
extension to the C90 standard, but the preferred mechanism to declare
variable-length types such as these ones is a flexible array
member [1], introduced in C99:
struct foo {
int stuff;
struct boo array[];
};
By making use of the mechanism above, we will get a compiler warning
in case the flexible array does not occur last in the structure, which
will help us prevent some kind of undefined behavior bugs from being
inadvertently introduced[3] to the codebase from now on.
Also, notice that, dynamic memory allocations won't be affected by
this change:
"Flexible array members have incomplete type, and so the sizeof operator
may not be applied. As a quirk of the original implementation of
zero-length arrays, sizeof evaluates to zero."[1]
This issue was found with the help of Coccinelle.
[1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
Signed-off-by: Paul Menzel <pmen...@molgen.mpg.de>
It gives the same size of structure either way.
Reviewed-by: Stefan Berger <stef...@linux.ibm.com>
---
src/std/tcg.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/src/std/tcg.h b/src/std/tcg.h
index 1cc1c92..1c9eeb4 100644
--- a/src/std/tcg.h
+++ b/src/std/tcg.h
@@ -524,7 +524,7 @@ struct TCG_EfiSpecIdEventStruct {
struct TCG_EfiSpecIdEventAlgorithmSize {
u16 algorithmId;
u16 digestSize;
- } digestSizes[0];
+ } digestSizes[];
/*
u8 vendorInfoSize;
u8 vendorInfo[0];
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