From de22924261ba7cb489afdbc8fe9dd6013da6f1cb Mon Sep 17 00:00:00 2001 From: Adhemerval Zanella Date: Thu, 21 Sep 2017 15:40:07 -0700 Subject: [PATCH] scratch_buffer: use union for internal buffer * lib/malloc/scratch_buffer.h (struct scratch_buffer): Use a union instead of a max_align_t array for __space, so that __space is the same size on all platforms. Problem reported by Florian Weimer in: https://sourceware.org/ml/libc-alpha/2017-09/msg00693.html Solution suggested by Andreas Schwab as discussed in: https://sourceware.org/ml/libc-alpha/2017-09/msg00695.html All uses changed. --- ChangeLog | 12 ++++++++++++ lib/malloc/scratch_buffer.h | 6 +++--- lib/malloc/scratch_buffer_grow_preserve.c | 4 ++-- 3 files changed, 17 insertions(+), 5 deletions(-) diff --git a/ChangeLog b/ChangeLog index 6a0b496..ecbab28 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,15 @@ +2017-09-21 Adhemerval Zanella + + scratch_buffer: use union for internal buffer + * lib/malloc/scratch_buffer.h (struct scratch_buffer): + Use an union instead of a max_align_t array for __space, + so that __space is the same size on all platforms. + Problem reported by Florian Weimer in: + https://sourceware.org/ml/libc-alpha/2017-09/msg00693.html + Solution suggested by Andreas Schwab as discussed in: + https://sourceware.org/ml/libc-alpha/2017-09/msg00695.html + All uses changed. + 2017-09-16 Paul Eggert manywarnings: port to GCC on 64-bit MS-Windows diff --git a/lib/malloc/scratch_buffer.h b/lib/malloc/scratch_buffer.h index 206b320..7d9020c 100644 --- a/lib/malloc/scratch_buffer.h +++ b/lib/malloc/scratch_buffer.h @@ -66,7 +66,7 @@ struct scratch_buffer { void *data; /* Pointer to the beginning of the scratch area. */ size_t length; /* Allocated space at the data pointer, in bytes. */ - max_align_t __space[(1023 + sizeof (max_align_t)) / sizeof (max_align_t)]; + union { max_align_t __a; char __c[1024]; } __space; }; /* Initializes *BUFFER so that BUFFER->data points to BUFFER->__space @@ -74,7 +74,7 @@ struct scratch_buffer { static inline void scratch_buffer_init (struct scratch_buffer *buffer) { - buffer->data = buffer->__space; + buffer->data = buffer->__space.__c; buffer->length = sizeof (buffer->__space); } @@ -82,7 +82,7 @@ scratch_buffer_init (struct scratch_buffer *buffer) static inline void scratch_buffer_free (struct scratch_buffer *buffer) { - if (buffer->data != buffer->__space) + if (buffer->data != buffer->__space.__c) free (buffer->data); } diff --git a/lib/malloc/scratch_buffer_grow_preserve.c b/lib/malloc/scratch_buffer_grow_preserve.c index cf55cf2..c752bdd 100644 --- a/lib/malloc/scratch_buffer_grow_preserve.c +++ b/lib/malloc/scratch_buffer_grow_preserve.c @@ -30,14 +30,14 @@ __libc_scratch_buffer_grow_preserve (struct scratch_buffer *buffer) size_t new_length = 2 * buffer->length; void *new_ptr; - if (buffer->data == buffer->__space) + if (buffer->data == buffer->__space.__c) { /* Move buffer to the heap. No overflow is possible because buffer->length describes a small buffer on the stack. */ new_ptr = malloc (new_length); if (new_ptr == NULL) return false; - memcpy (new_ptr, buffer->__space, buffer->length); + memcpy (new_ptr, buffer->__space.__c, buffer->length); } else { -- 2.7.4