[PATCH] [RFC] RAII auto_mpfr and autp_mpz

[Richard Biener <rguenther@suse.de>]

The following adds two RAII classes, one for mpz_t and one for mpfr_t
making object lifetime management easier.  Both formerly require
explicit initialization with {mpz,mpfr}_init and release with
{mpz,mpfr}_clear.

I've converted two example places (where lifetime is trivial).

I've sofar only build cc1 with the change.  Any comments?

Thanks,
Richard.

	* system.h (class auto_mpz): New,
	* realmpfr.h (class auto_mpfr): Likewise.
	* fold-const-call.cc (do_mpfr_arg1): Use auto_mpfr.
	(do_mpfr_arg2): Likewise.
	* tree-ssa-loop-niter.cc (bound_difference): Use auto_mpz;
---
 gcc/fold-const-call.cc     |  8 ++------
 gcc/realmpfr.h             | 15 +++++++++++++++
 gcc/system.h               | 14 ++++++++++++++
 gcc/tree-ssa-loop-niter.cc | 10 +---------
 4 files changed, 32 insertions(+), 15 deletions(-)

diff --git a/gcc/fold-const-call.cc b/gcc/fold-const-call.cc
index 43819c1f984..fa0b287cc8a 100644
--- a/gcc/fold-const-call.cc
+++ b/gcc/fold-const-call.cc
@@ -130,14 +130,12 @@ do_mpfr_arg1 (real_value *result,
 
   int prec = format->p;
   mpfr_rnd_t rnd = format->round_towards_zero ? MPFR_RNDZ : MPFR_RNDN;
-  mpfr_t m;
 
-  mpfr_init2 (m, prec);
+  auto_mpfr m (prec);
   mpfr_from_real (m, arg, MPFR_RNDN);
   mpfr_clear_flags ();
   bool inexact = func (m, m, rnd);
   bool ok = do_mpfr_ckconv (result, m, inexact, format);
-  mpfr_clear (m);
 
   return ok;
 }
@@ -224,14 +222,12 @@ do_mpfr_arg2 (real_value *result,
 
   int prec = format->p;
   mpfr_rnd_t rnd = format->round_towards_zero ? MPFR_RNDZ : MPFR_RNDN;
-  mpfr_t m;
 
-  mpfr_init2 (m, prec);
+  auto_mpfr m (prec);
   mpfr_from_real (m, arg1, MPFR_RNDN);
   mpfr_clear_flags ();
   bool inexact = func (m, arg0.to_shwi (), m, rnd);
   bool ok = do_mpfr_ckconv (result, m, inexact, format);
-  mpfr_clear (m);
 
   return ok;
 }
diff --git a/gcc/realmpfr.h b/gcc/realmpfr.h
index 5e032c05f25..2db2ecc94d4 100644
--- a/gcc/realmpfr.h
+++ b/gcc/realmpfr.h
@@ -24,6 +24,21 @@
 #include <mpfr.h>
 #include <mpc.h>
 
+class auto_mpfr
+{
+public:
+  auto_mpfr () { mpfr_init (m_mpfr); }
+  explicit auto_mpfr (mpfr_prec_t prec) { mpfr_init2 (m_mpfr, prec); }
+  ~auto_mpfr () { mpfr_clear (m_mpfr); }
+
+  operator mpfr_t& () { return m_mpfr; }
+
+  auto_mpfr (const auto_mpfr &) = delete;
+
+private:
+  mpfr_t m_mpfr;
+};
+
 /* Convert between MPFR and REAL_VALUE_TYPE.  The caller is
    responsible for initializing and clearing the MPFR parameter.  */
 
diff --git a/gcc/system.h b/gcc/system.h
index 64cd5a49258..99f6c410481 100644
--- a/gcc/system.h
+++ b/gcc/system.h
@@ -701,6 +701,20 @@ extern int vsnprintf (char *, size_t, const char *, va_list);
 /* Do not introduce a gmp.h dependency on the build system.  */
 #ifndef GENERATOR_FILE
 #include <gmp.h>
+
+class auto_mpz
+{
+public:
+  auto_mpz () { mpz_init (m_mpz); }
+  ~auto_mpz () { mpz_clear (m_mpz); }
+
+  operator mpz_t& () { return m_mpz; }
+
+  auto_mpz (const auto_mpz &) = delete;
+
+private:
+  mpz_t m_mpz;
+};
 #endif
 
 /* Get libiberty declarations.  */
diff --git a/gcc/tree-ssa-loop-niter.cc b/gcc/tree-ssa-loop-niter.cc
index dc4c7a418f6..dcfba2fc7ae 100644
--- a/gcc/tree-ssa-loop-niter.cc
+++ b/gcc/tree-ssa-loop-niter.cc
@@ -722,7 +722,6 @@ bound_difference (class loop *loop, tree x, tree y, bounds *bnds)
   tree type = TREE_TYPE (x);
   tree varx, vary;
   mpz_t offx, offy;
-  mpz_t minx, maxx, miny, maxy;
   int cnt = 0;
   edge e;
   basic_block bb;
@@ -754,19 +753,12 @@ bound_difference (class loop *loop, tree x, tree y, bounds *bnds)
     {
       /* Otherwise, use the value ranges to determine the initial
 	 estimates on below and up.  */
-      mpz_init (minx);
-      mpz_init (maxx);
-      mpz_init (miny);
-      mpz_init (maxy);
+      auto_mpz minx, maxx, miny, maxy;
       determine_value_range (loop, type, varx, offx, minx, maxx);
       determine_value_range (loop, type, vary, offy, miny, maxy);
 
       mpz_sub (bnds->below, minx, maxy);
       mpz_sub (bnds->up, maxx, miny);
-      mpz_clear (minx);
-      mpz_clear (maxx);
-      mpz_clear (miny);
-      mpz_clear (maxy);
     }
 
   /* If both X and Y are constants, we cannot get any more precise.  */
-- 
2.35.3