Flag to disable wchar support

Federico Terraneo fede.tft@hotmail.it
Tue Feb 9 14:54:00 GMT 2010


Hi,
I've been using newlib + libstdc++ for quite some time compiled with 
"--target=arm-elf", but I'm switching to "--target=arm-eabi" for better 
support of new Cortex M3 microcontrollers.

However, this change caused a large code size increase in C++ code (see 
below), and the problem seems related to newlib.
In practice, compiling newlib 1.18.0 with "--target=arm-eabi" causes the 
inclusion of some new functions to support wide charactes, like wprintf 
and wscanf (for the full list see below), and this triggers libstdc++ 
into including support for wide characters in iostream code, which is 
what causes the code size increase.

So I'm asking these two questions:
1) Is it "normal" that these additional functions are included only with 
"--target=arm-eabi" and not with "--target=arm-elf"?
2) Is there a way to disable wide character support?
I've tried "--disable-newlib-mb" but it didn't work.

For now I've temporarily fixed the problem by downgrading to newlib 
1.17.0 since it does not have these new functions and code size returned 
at acceptable levels, but I'd like to stay up to date with the latest 
newlib.

-------------------------------------------------------

An example program to show the difference in code size between arm-elf 
and arm-eabi

#include <iostream>
using namespace std;

int main()
{
	cout<<"Hello world"<<endl;
	string line;
	getline(cin,line);
	cout<<line;
}

arm-elf-g++ -mcpu=arm7tdmi -g -O0 -c arm_test.cpp
arm-elf-g++ -mcpu=arm7tdmi  -o arm_test arm_test.o
arm-elf-size arm_test
    text	   data	    bss	    dec	    hex	filename
  368320	   2648	   3880	 374848	  5b840	arm_test

arm-eabi-g++ -mcpu=arm7tdmi -g -O0 -c arm_test.cpp
arm-eabi-g++ -mcpu=arm7tdmi  -o arm_test arm_test.o
arm-eabi-size arm_test
    text	   data	    bss	    dec	    hex	filename
  504292	   2756	   7468	 514516	  7d9d4	arm_test

-------------------------------------------------------

The list of functions that are present only when compiling with 
"--target=arm-elf"

$ arm-eabi-ar -t /opt/arm-eabi/arm-eabi/lib/libc.a | sort > ~/libc-eabi.txt
$ arm-elf-ar -t /opt/arm-elf/arm-elf/lib/libc.a | sort > ~/libc-elf.txt
$ diff -U 0 libc-elf.txt libc-eabi.txt
--- libc-elf.txt	2010-02-07 11:22:50.000000000 +0100
+++ libc-eabi.txt	2010-02-07 11:22:41.000000000 +0100
@@ -99,0 +100 @@
+lib_a-fpurge.o
@@ -117,0 +119 @@
+lib_a-fwprintf.o
@@ -118,0 +121 @@
+lib_a-fwscanf.o
@@ -211,0 +215 @@
+lib_a-mbsnrtowcs.o
@@ -224,0 +229 @@
+lib_a-mkdirr.o
@@ -269,0 +275 @@
+lib_a-sb_charsets.o
@@ -283,0 +290 @@
+lib_a-sf_fpclassify.o
@@ -292,0 +300 @@
+lib_a-s_fpclassify.o
@@ -350,0 +359 @@
+lib_a-strtold.o
@@ -360,0 +370,2 @@
+lib_a-svfiwprintf.o
+lib_a-svfiwscanf.o
@@ -362,0 +374,2 @@
+lib_a-svfwprintf.o
+lib_a-svfwscanf.o
@@ -363,0 +377,2 @@
+lib_a-swprintf.o
+lib_a-swscanf.o
@@ -395 +409,0 @@
-lib_a-_tolower.o
@@ -397 +410,0 @@
-lib_a-_toupper.o
@@ -423,0 +437,2 @@
+lib_a-vfiwprintf.o
+lib_a-vfiwscanf.o
@@ -425,0 +441,2 @@
+lib_a-vfwprintf.o
+lib_a-vfwscanf.o
@@ -435,0 +453,4 @@
+lib_a-vswprintf.o
+lib_a-vswscanf.o
+lib_a-vwprintf.o
+lib_a-vwscanf.o
@@ -439,0 +461 @@
+lib_a-wcscasecmp.o
@@ -445,0 +468,2 @@
+lib_a-wcsdup.o
+lib_a-wcsftime.o
@@ -448,0 +473 @@
+lib_a-wcsncasecmp.o
@@ -452,0 +478 @@
+lib_a-wcsnrtombs.o
@@ -457,0 +484 @@
+lib_a-wcstod.o
@@ -458,0 +486 @@
+lib_a-wcstold.o
@@ -479,0 +508 @@
+lib_a-wprintf.o
@@ -480,0 +510 @@
+lib_a-wscanf.o



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