Add compiler warning flags and fix warnings

Mostly signed vs unsigned comparisons
Signed-off-by: Keith Packard <keithp@keithp.com>

configure.ac

@@ -25,6 +25,7 @@ AC_INIT([libXfont], [1.5.1],
 	[https://bugs.freedesktop.org/enter_bug.cgi?product=xorg], [libXfont])
 AC_CONFIG_SRCDIR([Makefile.am])
 AC_CONFIG_HEADERS([config.h include/X11/fonts/fontconf.h])
+AC_CONFIG_MACRO_DIR([m4])
 
 # Initialize Automake
 AM_INIT_AUTOMAKE([foreign dist-bzip2])
@@ -57,6 +58,27 @@ AC_CHECK_FUNCS([poll readlink])
 # must first be located explicitly.
 PKG_PROG_PKG_CONFIG
 
+with_cflags=""
+if test "x$GCC" = "xyes"; then
+	CC_CHECK_FLAGS_APPEND([with_cflags], [CFLAGS], [\
+				-Wall \
+				-Wextra \
+				-Wno-sign-compare \
+				-Wno-missing-field-initializers \
+				-Wno-unused-parameter \
+				-Wstrict-prototypes \
+				-Wmissing-prototypes \
+				-fvisibility=hidden \
+				-pipe \
+				-fno-strict-aliasing \
+				-ffunction-sections \
+				-fdata-sections \
+				-fno-strict-aliasing \
+				-fdiagnostics-show-option \
+				-fno-common])
+fi
+AC_SUBST([GCC_CFLAGS], $with_cflags)
+
 #
 # select libraries to include
 #
@@ -217,6 +239,8 @@ case $host_os in
         OS_CFLAGS=
         ;;
 esac
+OS_CFLAGS="$OS_CFLAGS $GCC_CFLAGS"
+
 AC_SUBST([OS_CFLAGS])
 
 AC_CONFIG_FILES([Makefile

src/FreeType/ftfuncs.c

@@ -474,7 +474,7 @@ FreeTypeOpenInstance(FTInstancePtr *instance_return, FTFacePtr face,
     if( FT_IS_SFNT( face->face ) ) {
 #if 1
         FT_F26Dot6  tt_char_width, tt_char_height, tt_dim_x, tt_dim_y;
-        FT_UInt     nn;
+        FT_Int     nn;
 
         instance->strike_index=0xFFFFU;
 
@@ -1454,7 +1454,7 @@ FreeTypeRasteriseGlyph(unsigned idx, int flags, CharInfoPtr tgp,
 	}
 	for( i = MAX(0, dy) ; i<ht ; i++ ){
 	    int prev_jj,jj;
-	    if( bitmap->rows <= i-dy ) break;
+	    if( bitmap->rows <= (unsigned) (i-dy) ) break;
 	    current_buffer=(unsigned char *)(bitmap->buffer+bitmap->pitch*(i-dy));
 	    current_raster=(unsigned char *)(raster+i*bpr);
 	    j       = MAX(0,div_dx);
@@ -2985,13 +2985,13 @@ ft_compute_bounds(FTFontPtr font, FontInfoPtr pinfo, FontScalablePtr vals )
           c = row<<8|col;
           flags=0;
           if ( !force_c_outside ) {
-              if ( c <= instance->ttcap.forceConstantSpacingEnd
-		   && instance->ttcap.forceConstantSpacingBegin <= c )
+	      if ( (signed) c <= instance->ttcap.forceConstantSpacingEnd
+		   && instance->ttcap.forceConstantSpacingBegin <= (signed) c )
                   flags|=FT_FORCE_CONSTANT_SPACING;
           }
           else {        /* for GB18030 proportional */
-              if ( c <= instance->ttcap.forceConstantSpacingEnd
-		   || instance->ttcap.forceConstantSpacingBegin <= c )
+              if ( (signed) c <= instance->ttcap.forceConstantSpacingEnd
+		   || instance->ttcap.forceConstantSpacingBegin <= (signed) c )
                   flags|=FT_FORCE_CONSTANT_SPACING;
           }
 #if 0

src/bitmap/bdfread.c

@@ -298,7 +298,7 @@ bdfReadCharacters(FontFilePtr file, FontPtr pFont, bdfFileState *pState,
 	bdfError("invalid number of CHARS in BDF file\n");
 	return (FALSE);
     }
-    if (nchars > INT32_MAX / sizeof(CharInfoRec)) {
+    if (nchars > (signed) (INT32_MAX / sizeof(CharInfoRec))) {
 	bdfError("Couldn't allocate pCI (%d*%d)\n", nchars,
 		 (int) sizeof(CharInfoRec));
 	goto BAILOUT;
@@ -631,7 +631,7 @@ bdfReadProperties(FontFilePtr file, FontPtr pFont, bdfFileState *pState)
     }
     if ((sscanf((char *) line, "STARTPROPERTIES %d", &nProps) != 1) ||
 	(nProps <= 0) ||
-	(nProps > ((INT32_MAX / sizeof(FontPropRec)) - BDF_GENPROPS))) {
+	(nProps > (signed) ((INT32_MAX / sizeof(FontPropRec)) - BDF_GENPROPS))) {
 	bdfError("bad 'STARTPROPERTIES'\n");
 	return (FALSE);
     }

src/bitmap/pcfread.c

@@ -487,7 +487,6 @@ pcfReadFont(FontPtr pFont, FontFilePtr file,
     for (i = 0; i < GLYPHPADOPTIONS; i++) {
 	bitmapSizes[i] = pcfGetINT32(file, format);
 	if (IS_EOF(file)) goto Bail;
-	if (bitmapSizes[i] < 0) goto Bail;
     }
 
     sizebitmaps = bitmapSizes[PCF_GLYPH_PAD_INDEX(format)];

src/fc/fstrans.c

@@ -26,3 +26,5 @@
 #define FONT_t
 #define TRANS_CLIENT
 #include <X11/Xtrans/transport.c>
+/* inhibit warning about is_numeric */
+static inline void foo(void) { (void) is_numeric("a"); }