> > Hello.
> >
> > As noticed in the PR, it's quite tricky to not run malloc (or calloc)
> > in context of libgcov. I'm suggesting a new approach where we'll first
> > use the pre-allocated static buffer in hope that malloc function is
> > initialized
> > and so every call to calloc can happen. That's why I increased number of KVP
> > to 64 and I believe one reaches malloc pretty soon in an application run.
> >
> > Patch can bootstrap on x86_64-linux-gnu and survives regression tests.
> >
> > Ready to be installed?
> > Thanks,
> > Martin
> >
> > gcc/ChangeLog:
> >
> > PR gcov-profile/97461
> > * gcov-io.h (GCOV_PREALLOCATED_KVP): Pre-allocate 64
> > static counters.
> >
> > libgcc/ChangeLog:
> >
> > PR gcov-profile/97461
> > * libgcov.h (gcov_counter_add): Use first static counters
> > as it should help to have malloc wrappers set up.
> >
> > gcc/testsuite/ChangeLog:
> >
> > PR gcov-profile/97461
> > * gcc.dg/tree-prof/pr97461.c: New test.
Looks reasonable, but I do not like very much the non-configurable
preallocation since libgcov was meant to be useful for embedded targets
and not consume too much. I guess we could handle that incrementally,
how the llvm's option for preallocated pool size is implemented?
Honza
> > ---
> > gcc/gcov-io.h | 2 +-
> > gcc/testsuite/gcc.dg/tree-prof/pr97461.c | 58 ++++++++++++++++++++++++
> > libgcc/libgcov.h | 24 +++-------
> > 3 files changed, 65 insertions(+), 19 deletions(-)
> > create mode 100644 gcc/testsuite/gcc.dg/tree-prof/pr97461.c
> >
> > diff --git a/gcc/gcov-io.h b/gcc/gcov-io.h
> > index 4dba01c78ce..4e95c7c82ee 100644
> > --- a/gcc/gcov-io.h
> > +++ b/gcc/gcov-io.h
> > @@ -293,7 +293,7 @@ GCOV_COUNTERS
> > #define GCOV_TOPN_MAXIMUM_TRACKED_VALUES 32
> >
> > /* Number of pre-allocated gcov_kvp structures. */
> > -#define GCOV_PREALLOCATED_KVP 16
> > +#define GCOV_PREALLOCATED_KVP 64
> >
> > /* Convert a counter index to a tag. */
> > #define GCOV_TAG_FOR_COUNTER(COUNT) \
> > diff --git a/gcc/testsuite/gcc.dg/tree-prof/pr97461.c
> > b/gcc/testsuite/gcc.dg/tree-prof/pr97461.c
> > new file mode 100644
> > index 00000000000..8d21a3ef421
> > --- /dev/null
> > +++ b/gcc/testsuite/gcc.dg/tree-prof/pr97461.c
> > @@ -0,0 +1,58 @@
> > +/* PR gcov-profile/97461 */
> > +/* { dg-options "-O2 -ldl" } */
> > +
> > +#define _GNU_SOURCE
> > +
> > +#include <stdio.h>
> > +#include <stdlib.h>
> > +#include <string.h>
> > +
> > +static int malloc_depth = 0;
> > +
> > +static char memory[128* 1024];
> > +static size_t memory_p = 0;
> > +
> > +void f1(void) {}
> > +void f2(void) {}
> > +
> > +typedef void (*fun_t)(void);
> > +static const fun_t funs[2] = { f1, f2, };
> > +
> > +static void * malloc_impl(size_t size) {
> > + void * r = &memory[memory_p];
> > + memory_p += size;
> > +
> > + // force TOPN profile
> > + funs[size % 2]();
> > + return r;
> > +}
> > +
> > +// Override default malloc, check it it get s called recursively
> > +void * malloc(size_t size) {
> > + // Must not be called recursively. Malloc implementation does not
> > support it.
> > + if (malloc_depth != 0) __builtin_trap();
> > +
> > + ++malloc_depth;
> > + void * r = malloc_impl(size);
> > + --malloc_depth;
> > + return r;
> > +}
> > +
> > +// Called from gcov
> > +void *calloc(size_t nmemb, size_t size) {
> > + // Must not be called recursively. Malloc implementation does not
> > support it.
> > + if (malloc_depth != 0) __builtin_trap();
> > +
> > + ++malloc_depth;
> > + void * r = malloc_impl(size * nmemb);
> > + memset(r, 0, size * nmemb);
> > + --malloc_depth;
> > + return r;
> > +}
> > +
> > +void free(void *ptr){}
> > +
> > +int main() {
> > + void * p = malloc(8);
> > + return p != 0 ? 0 : 1;
> > +}
> > diff --git a/libgcc/libgcov.h b/libgcc/libgcov.h
> > index 8be5bebcac0..e70cf63b414 100644
> > --- a/libgcc/libgcov.h
> > +++ b/libgcc/libgcov.h
> > @@ -404,22 +404,16 @@ gcov_counter_add (gcov_type *counter, gcov_type value,
> > *counter += value;
> > }
> >
> > -/* Allocate gcov_kvp from heap. If we are recursively called, then
> > allocate
> > - it from a list of pre-allocated pool. */
> > +/* Allocate gcov_kvp from statically pre-allocated pool,
> > + or use heap otherwise. */
> >
> > static inline struct gcov_kvp *
> > allocate_gcov_kvp (void)
> > {
> > struct gcov_kvp *new_node = NULL;
> >
> > - static
> > -#if defined(HAVE_CC_TLS)
> > -__thread
> > -#endif
> > - volatile unsigned in_recursion ATTRIBUTE_UNUSED = 0;
> > -
> > #if !defined(IN_GCOV_TOOL) && !defined(L_gcov_merge_topn)
> > - if (__builtin_expect (in_recursion, 0))
> > + if (__gcov_kvp_pool_index < GCOV_PREALLOCATED_KVP)
> > {
> > unsigned index;
> > #if GCOV_SUPPORTS_ATOMIC
> > @@ -430,17 +424,11 @@ __thread
> > #endif
> > if (index < GCOV_PREALLOCATED_KVP)
> > new_node = &__gcov_kvp_pool[index];
> > - else
> > - /* Do not crash in the situation. */
> > - return NULL;
> > }
> > - else
> > #endif
> > - {
> > - in_recursion = 1;
> > - new_node = (struct gcov_kvp *)xcalloc (1, sizeof (struct gcov_kvp));
> > - in_recursion = 0;
> > - }
> > +
> > + if (new_node == NULL)
> > + new_node = (struct gcov_kvp *)xcalloc (1, sizeof (struct gcov_kvp));
> >
> > return new_node;
> > }
>
