snprintf in write_float.def

[FX]

Hi all,

While reducing PR36200, I was looking at libgfortran/io/ 
write_float.def, and after having refreshed my memory about printf  
formats, it seems to me that what we're doing in DTOA and DTOAL is  
unsafe: the "e" format expects an argument of type double, and yet  
when used for real(kind=4), we'll happily pass it a "float". So, am I  
overlooking something or should we apply the patch below (which casts  
values to "double" or "long double")? I suspect there is more to it  
that I saw, because we'd see a large number of failures otherwise.  
So, comments welcome.

FX



Index: io/write_float.def
===================================================================
--- io/write_float.def  (revision 135088)
+++ io/write_float.def  (working copy)
@@ -708,21 +708,21 @@ OUTPUT_FLOAT_FMT_G(16)

  #define DTOA \
  snprintf (buffer, size, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
-         "e", ndigits - 1, tmp);
+         "e", ndigits - 1, (double) tmp);

  #define DTOAL \
  snprintf (buffer, size, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
-         "Le", ndigits - 1, tmp);
+         "Le", ndigits - 1, (long double) tmp);

  #else

  #define DTOA \
  sprintf (buffer, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
-        "e", ndigits - 1, tmp);
+        "e", ndigits - 1, (double) tmp);

  #define DTOAL \
  sprintf (buffer, "%+-#" STR(MIN_FIELD_WIDTH) ".*" \
-        "Le", ndigits - 1, tmp);
+        "Le", ndigits - 1, (long double) tmp);

  #endif



-- 
François-Xavier Coudert
http://www.homepages.ucl.ac.uk/~uccafco/