Perl_sv_vcatpvfn_flags: handle %.NNNg case earlier

In the main loop, we look for %.NNNg and handle it specially.
Change it so that the special-case is only used when precis is small
enough to that it fits in the local ebuf[] rather than the malloced
PL_efloatbuf. This allows the check for this special case to be done
earlier with less redundant calculations.

diff --git a/sv.c b/sv.c
index 73e58e5..0e4bdba 100644 (file)
--- a/sv.c
+++ b/sv.c
@@ -12622,7 +12622,6 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
        case 'a': case 'A':
 
         {
-            bool   can_be_special; /* candidate for special-case-handling */
             STRLEN radix_len;  /* SvCUR(PL_numeric_radix_sv) */
             STRLEN float_need; /* what PL_efloatsize needs to become */
             bool hexfp;        /* hexadecimal floating point? */
@@ -12720,17 +12719,16 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
                 break;
             }
 
-            /* a candidate for special-casing: %.0f and %.NNNg */
-            can_be_special = ( !(width || left || plus || alt)
-                              && fill != '0'
-                              && has_precis
-                              && intsize != 'q');
-
             /* special-case "%.0f" */
-            if (can_be_special && c == 'f' && !precis) {
-                if ((eptr = F0convert(nv, ebuf + sizeof ebuf, &elen)))
-                    goto float_concat_no_utf8;
-            }
+            if (   c == 'f'
+                && !precis
+                && has_precis
+                && !(width || left || plus || alt)
+                && fill != '0'
+                && intsize != 'q'
+                && ((eptr = F0convert(nv, ebuf + sizeof ebuf, &elen)))
+            )
+                goto float_concat_no_utf8;
 
             /* Determine the buffer size needed for the various
              * floating-point formats.
@@ -12844,6 +12842,26 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
                     float_need += digits;
                 }
            }
+            /* special-case "%.<number>g" if it will fit in ebuf */
+            else if (c == 'g'
+                && precis   /* See earlier comment about buggy Gconvert
+                               when digits, aka precis, is 0  */
+                && has_precis
+                /* check, in manner not involving wrapping, that it will
+                 * fit in ebuf  */
+                && float_need < sizeof(ebuf)
+                && sizeof(ebuf) - float_need > precis
+                && !(width || left || plus || alt)
+                && fill != '0'
+                && intsize != 'q'
+            ) {
+                STORE_LC_NUMERIC_SET_TO_NEEDED();
+                SNPRINTF_G(fv, ebuf, sizeof(ebuf), precis);
+                elen = strlen(ebuf);
+                eptr = ebuf;
+                goto float_concat;
+           }
+
 
             {
                 STRLEN pr = has_precis ? precis : 6; /* known default */
@@ -12874,21 +12892,6 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
                PL_efloatbuf[0] = '\0';
            }
 
-            /* special-case "%.<number>g" */
-            if (can_be_special) {
-               /* See earlier comment about buggy Gconvert when digits,
-                  aka precis is 0  */
-               if ( c == 'g' && precis ) {
-                    STORE_LC_NUMERIC_SET_TO_NEEDED();
-                    SNPRINTF_G(fv, PL_efloatbuf, PL_efloatsize, precis);
-                   /* May return an empty string for digits==0 */
-                   if (*PL_efloatbuf) {
-                       elen = strlen(PL_efloatbuf);
-                       goto float_concat;
-                   }
-                }
-           }
-
             if (UNLIKELY(hexfp)) {
                 elen = S_format_hexfp(aTHX_ PL_efloatbuf, PL_efloatsize, c,
                                 nv, fv, has_precis, precis, width,
@@ -12970,9 +12973,10 @@ Perl_sv_vcatpvfn_flags(pTHX_ SV *const sv, const char *const pat, const STRLEN p
                 GCC_DIAG_RESTORE;
            }
 
-         float_concat:
            eptr = PL_efloatbuf;
 
+         float_concat:
+
             /* Since floating-point formats do their own formatting and
              * padding, we skip the main block of code at the end of this
              * loop which handles appending eptr to sv, and do our own