build: Add scripts/makefile.c89; update other makefiles

Add scripts/makefile.c89 and refactor scripts/makefile.emcc,
scripts/makefile.clang and scripts/makefile.gcc

Refactor variable definitions inside scripts/makefile.clang,
scripts/makefile.gcc and scripts/makefile.emcc, and start using
the option `-pedantic-errors` unconditionally. This option was
first implemented in GCC version 3.1, and it was available in
Clang and in other Clang-based compilers (e.g. Emscripten) from
the beginning.

Add scripts/makefile.c89, derived from the above makefiles, but
with `-pedantic-errors -std=c89`. We aren't enabling the C89 level
by default, to avoid any incompatibility, whether intentional or
accidental, with the compiler's default language level. However,
we are still continuing to support C89 in the 'libpng16' branch,
and this special makefile can be used for testing purposes.

scripts/makefile.c89

@@ -0,0 +1,97 @@
+# makefile for libpng using an ANSI C89 compiler
+# Copyright (C) 2000, 2014, 2019-2025 Cosmin Truta
+# Copyright (C) 2008, 2014 Glenn Randers-Pehrson
+# Copyright (C) 1995 Guy Eric Schalnat, Group 42, Inc.
+#
+# This code is released under the libpng license.
+# For conditions of distribution and use, see the disclaimer
+# and license in png.h
+
+# Location of the zlib library and include files
+ZLIBINC = ../zlib
+ZLIBLIB = ../zlib
+
+# Compiler, linker, lib and other tools
+#CC = c89
+CC = cc
+LD = $(CC)
+AR = ar
+RANLIB = ranlib
+CP = cp
+RM_F = rm -f
+
+# Compiler and linker flags
+NOHWOPT = -DPNG_ARM_NEON_OPT=0 -DPNG_MIPS_MSA_OPT=0 \
+          -DPNG_POWERPC_VSX_OPT=0 -DPNG_INTEL_SSE_OPT=0
+STDC = -pedantic-errors -std=c89
+WARN = -Wall -Wextra -Wundef
+WARNMORE = -Wcast-align -Wconversion -Wshadow -Wpointer-arith -Wwrite-strings \
+           -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes
+LOCAL_CPPFLAGS = $(NOHWOPT)
+CPPFLAGS = -I$(ZLIBINC) # -DPNG_DEBUG=5
+ALL_CPPFLAGS = $(LOCAL_CPPFLAGS) $(CPPFLAGS)
+LOCAL_CFLAGS = $(STDC) $(WARN) # $(WARNMORE)
+CFLAGS = -O2 # -g
+ALL_CFLAGS = $(LOCAL_CFLAGS) $(CFLAGS)
+ARFLAGS = rc
+LDFLAGS = -L$(ZLIBLIB) # -g
+LIBS = -lz -lm
+
+# File extensions
+EXEEXT =
+
+# Pre-built configuration
+# See scripts/pnglibconf.mak for more options
+PNGLIBCONF_H_PREBUILT = scripts/pnglibconf.h.prebuilt
+
+# File lists
+OBJS = png.o pngerror.o pngget.o pngmem.o pngpread.o \
+       pngread.o pngrio.o pngrtran.o pngrutil.o pngset.o \
+       pngtrans.o pngwio.o pngwrite.o pngwtran.o pngwutil.o
+
+# Targets
+all: static
+
+pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
+	$(CP) $(PNGLIBCONF_H_PREBUILT) $@
+
+.c.o:
+	$(CC) -c $(ALL_CPPFLAGS) $(ALL_CFLAGS) -o $@ $*.c
+
+static: libpng.a pngtest$(EXEEXT)
+
+shared:
+	@echo This is a generic makefile that cannot create shared libraries.
+	@echo Please use a configuration that is specific to your platform.
+	@false
+
+libpng.a: $(OBJS)
+	$(AR) $(ARFLAGS) $@ $(OBJS)
+	$(RANLIB) $@
+
+test: pngtest$(EXEEXT)
+	./pngtest$(EXEEXT)
+
+pngtest$(EXEEXT): pngtest.o libpng.a
+	$(LD) $(LDFLAGS) -o $@ pngtest.o libpng.a $(LIBS)
+
+clean:
+	$(RM_F) *.o libpng.a pngtest$(EXEEXT) pngout.png pnglibconf.h
+
+png.o:      png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngerror.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngget.o:   png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngmem.o:   png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngpread.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngread.o:  png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrio.o:   png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrtran.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngrutil.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngset.o:   png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngtrans.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwio.o:   png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwrite.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwtran.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+pngwutil.o: png.h pngconf.h pnglibconf.h pngpriv.h pngstruct.h pnginfo.h pngdebug.h
+
+pngtest.o:  png.h pngconf.h pnglibconf.h

scripts/makefile.clang

@@ -1,5 +1,5 @@
 # makefile for libpng using clang (generic, static library)
-# Copyright (C) 2000, 2014, 2019-2024 Cosmin Truta
+# Copyright (C) 2000, 2014, 2019-2025 Cosmin Truta
 # Copyright (C) 2008, 2014 Glenn Randers-Pehrson
 # Copyright (C) 1995 Guy Eric Schalnat, Group 42, Inc.
 #
@@ -21,13 +21,17 @@ RM_F = rm -f
 
 # Compiler and linker flags
 NOHWOPT = -DPNG_ARM_NEON_OPT=0 -DPNG_MIPS_MSA_OPT=0 \
-	-DPNG_POWERPC_VSX_OPT=0 -DPNG_INTEL_SSE_OPT=0
-WARNMORE = -Wwrite-strings -Wpointer-arith -Wshadow \
-	-Wmissing-declarations -Wtraditional -Wcast-align \
-	-Wstrict-prototypes -Wmissing-prototypes # -Wconversion
-DEFS = $(NOHWOPT)
-CPPFLAGS = -I$(ZLIBINC) $(DEFS) # -DPNG_DEBUG=5
-CFLAGS = -O2 -Wall -Wextra -Wundef # $(WARNMORE) -g
+          -DPNG_POWERPC_VSX_OPT=0 -DPNG_INTEL_SSE_OPT=0
+STDC = -pedantic-errors # -std=c99
+WARN = -Wall -Wextra -Wundef
+WARNMORE = -Wcast-align -Wconversion -Wshadow -Wpointer-arith -Wwrite-strings \
+           -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes
+LOCAL_CPPFLAGS = $(NOHWOPT)
+CPPFLAGS = -I$(ZLIBINC) # -DPNG_DEBUG=5
+ALL_CPPFLAGS = $(LOCAL_CPPFLAGS) $(CPPFLAGS)
+LOCAL_CFLAGS = $(STDC) $(WARN) # $(WARNMORE)
+CFLAGS = -O2 # -g
+ALL_CFLAGS = $(LOCAL_CFLAGS) $(CFLAGS)
 ARFLAGS = rc
 LDFLAGS = -L$(ZLIBLIB) # -g
 LIBS = -lz -lm
@@ -51,7 +55,7 @@ pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $(PNGLIBCONF_H_PREBUILT) $@
 
 .c.o:
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
+	$(CC) -c $(ALL_CPPFLAGS) $(ALL_CFLAGS) -o $@ $*.c
 
 static: libpng.a pngtest$(EXEEXT)
 

scripts/makefile.emcc

@@ -1,5 +1,5 @@
 # makefile for libpng using emscripten
-# Copyright (C) 2000, 2014, 2019-2024 Cosmin Truta
+# Copyright (C) 2000, 2014, 2019-2025 Cosmin Truta
 # Copyright (C) 2021 Kirk Roerig
 # Copyright (C) 2008, 2014 Glenn Randers-Pehrson
 # Copyright (C) 1995 Guy Eric Schalnat, Group 42, Inc.
@@ -20,8 +20,16 @@ RANLIB = emranlib
 CP = cp
 RM_F = rm -f
 
+STDC = -pedantic-errors # -std=c99
+WARN = -Wall -Wextra -Wundef
+WARNMORE = -Wcast-align -Wconversion -Wshadow -Wpointer-arith -Wwrite-strings \
+           -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes
+LOCAL_CPPFLAGS =
 CPPFLAGS = -I$(ZLIBINC) # -DPNG_DEBUG=5
-CFLAGS = -O2 -Wall -Wextra -Wundef
+ALL_CPPFLAGS = $(LOCAL_CPPFLAGS) $(CPPFLAGS)
+LOCAL_CFLAGS = $(STDC) $(WARN) # $(WARNMORE)
+CFLAGS = -O2
+ALL_CFLAGS = $(LOCAL_CFLAGS) $(CFLAGS)
 ARFLAGS = rc
 LDFLAGS = -L$(ZLIBLIB)
 PNGTEST_LDFLAGS = --preload-file=pngtest.png
@@ -43,7 +51,7 @@ pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $(PNGLIBCONF_H_PREBUILT) $@
 
 .c.o:
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
+	$(CC) -c $(ALL_CPPFLAGS) $(ALL_CFLAGS) -o $@ $*.c
 
 static: libpng.a pngtest
 

scripts/makefile.gcc

@@ -1,5 +1,5 @@
 # makefile for libpng using gcc (generic, static library)
-# Copyright (C) 2000, 2014, 2019-2024 Cosmin Truta
+# Copyright (C) 2000, 2014, 2019-2025 Cosmin Truta
 # Copyright (C) 2008, 2014 Glenn Randers-Pehrson
 # Copyright (C) 1995 Guy Eric Schalnat, Group 42, Inc.
 #
@@ -21,13 +21,17 @@ RM_F = rm -f
 
 # Compiler and linker flags
 NOHWOPT = -DPNG_ARM_NEON_OPT=0 -DPNG_MIPS_MSA_OPT=0 \
-	-DPNG_POWERPC_VSX_OPT=0 -DPNG_INTEL_SSE_OPT=0
-WARNMORE = -Wwrite-strings -Wpointer-arith -Wshadow \
-	-Wmissing-declarations -Wtraditional -Wcast-align \
-	-Wstrict-prototypes -Wmissing-prototypes # -Wconversion
-DEFS = $(NOHWOPT)
-CPPFLAGS = -I$(ZLIBINC) $(DEFS) # -DPNG_DEBUG=5
-CFLAGS = -O2 -Wall -Wextra -Wundef # $(WARNMORE) -g
+          -DPNG_POWERPC_VSX_OPT=0 -DPNG_INTEL_SSE_OPT=0
+STDC = -pedantic-errors # -std=c99
+WARN = -Wall -Wextra -Wundef
+WARNMORE = -Wcast-align -Wconversion -Wshadow -Wpointer-arith -Wwrite-strings \
+           -Wmissing-declarations -Wmissing-prototypes -Wstrict-prototypes
+LOCAL_CPPFLAGS = $(NOHWOPT)
+CPPFLAGS = -I$(ZLIBINC) # -DPNG_DEBUG=5
+ALL_CPPFLAGS = $(LOCAL_CPPFLAGS) $(CPPFLAGS)
+LOCAL_CFLAGS = $(STDC) $(WARN) # $(WARNMORE)
+CFLAGS = -O2 # -g
+ALL_CFLAGS = $(LOCAL_CFLAGS) $(CFLAGS)
 ARFLAGS = rc
 LDFLAGS = -L$(ZLIBLIB) # -g
 LIBS = -lz -lm
@@ -51,7 +55,7 @@ pnglibconf.h: $(PNGLIBCONF_H_PREBUILT)
 	$(CP) $(PNGLIBCONF_H_PREBUILT) $@
 
 .c.o:
-	$(CC) -c $(CPPFLAGS) $(CFLAGS) -o $@ $<
+	$(CC) -c $(ALL_CPPFLAGS) $(ALL_CFLAGS) -o $@ $*.c
 
 static: libpng.a pngtest$(EXEEXT)