Remove GCC7.1 arithmetic overflow fixup

This removes pragmas and the controlling code that quelled warnings
generated by GCC7.1 (only) with -Wstrict-overflow=3 and possibly other
levels.  Tested with GCC13.2, GCC7.1 is no longer the current version of
GCC7 (GCC7.5) and GCC7.1 was replaced by GCC7.2 on August 14, 2017.

Signed-off-by: John Bowler <jbowler@acm.org>

1 files changed, 0 insertions, 44 deletions

diff --git a/png.c b/png.c
index 0dbb234e5..1bcf042af 100644
--- a/png.c
+++ b/png.c
@@ -16,26 +16,6 @@
 /* Generate a compiler error if there is an old png.h in the search path. */
 typedef png_libpng_version_1_6_41_git Your_png_h_is_not_version_1_6_41_git;
 
-#ifdef __GNUC__
-/* The version tests may need to be added to, but the problem warning has
- * consistently been fixed in GCC versions which obtain wide-spread release.
- * The problem is that many versions of GCC rearrange comparison expressions in
- * the optimizer in such a way that the results of the comparison will change
- * if signed integer overflow occurs.  Such comparisons are not permitted in
- * ANSI C90, however GCC isn't clever enough to work out that that do not occur
- * below in png_ascii_from_fp and png_muldiv, so it produces a warning with
- * -Wextra.  Unfortunately this is highly dependent on the optimizer and the
- * machine architecture so the warning comes and goes unpredictably and is
- * impossible to "fix", even were that a good idea.
- */
-#if __GNUC__ == 7 && __GNUC_MINOR__ == 1
-#define GCC_STRICT_OVERFLOW 1
-#endif /* GNU 7.1.x */
-#endif /* GNU */
-#ifndef GCC_STRICT_OVERFLOW
-#define GCC_STRICT_OVERFLOW 0
-#endif
-
 /* Tells libpng that we have already handled the first "num_bytes" bytes
  * of the PNG file signature.  If the PNG data is embedded into another
  * stream we can set num_bytes = 8 so that libpng will not attempt to read
@@ -2890,14 +2870,6 @@ png_pow10(int power)
 /* Function to format a floating point value in ASCII with a given
  * precision.
  */
-#if GCC_STRICT_OVERFLOW
-#pragma GCC diagnostic push
-/* The problem arises below with exp_b10, which can never overflow because it
- * comes, originally, from frexp and is therefore limited to a range which is
- * typically +/-710 (log2(DBL_MAX)/log2(DBL_MIN)).
- */
-#pragma GCC diagnostic warning "-Wstrict-overflow=2"
-#endif /* GCC_STRICT_OVERFLOW */
 void /* PRIVATE */
 png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size,
     double fp, unsigned int precision)
@@ -3219,10 +3191,6 @@ png_ascii_from_fp(png_const_structrp png_ptr, png_charp ascii, size_t size,
    /* Here on buffer too small. */
    png_error(png_ptr, "ASCII conversion buffer too small");
 }
-#if GCC_STRICT_OVERFLOW
-#pragma GCC diagnostic pop
-#endif /* GCC_STRICT_OVERFLOW */
-
 #  endif /* FLOATING_POINT */
 
 #  ifdef PNG_FIXED_POINT_SUPPORTED
@@ -3335,15 +3303,6 @@ png_fixed(png_const_structrp png_ptr, double fp, png_const_charp text)
  * the nearest .00001).  Overflow and divide by zero are signalled in
  * the result, a boolean - true on success, false on overflow.
  */
-#if GCC_STRICT_OVERFLOW /* from above */
-/* It is not obvious which comparison below gets optimized in such a way that
- * signed overflow would change the result; looking through the code does not
- * reveal any tests which have the form GCC complains about, so presumably the
- * optimizer is moving an add or subtract into the 'if' somewhere.
- */
-#pragma GCC diagnostic push
-#pragma GCC diagnostic warning "-Wstrict-overflow=2"
-#endif /* GCC_STRICT_OVERFLOW */
 int
 png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
     png_int_32 divisor)
@@ -3458,9 +3417,6 @@ png_muldiv(png_fixed_point_p res, png_fixed_point a, png_int_32 times,
 
    return 0;
 }
-#if GCC_STRICT_OVERFLOW
-#pragma GCC diagnostic pop
-#endif /* GCC_STRICT_OVERFLOW */
 #endif /* READ_GAMMA || INCH_CONVERSIONS */
 
 #if defined(PNG_READ_GAMMA_SUPPORTED) || defined(PNG_INCH_CONVERSIONS_SUPPORTED)