Step to UEFI Shell (6) ---- Shell 中使用 Float

如果你在Shell下直接使用 Float 或者 Double 在编译的时候会遇到这样的问题

Architecture(s) = IA32
Build target = DEBUG
Toolchain = VS2008

Active Platform = c:\edk2\Nt32Pkg\Nt32Pkg.dsc
Flash Image Definition = c:\edk2\Nt32Pkg\Nt32Pkg.fdf

Processing meta-data ... done!
"C:\Program Files\Microsoft Visual Studio 9.0\Vc\bin\link.exe" /out:"c:\edk2\Build\NT32\DEBUG_VS2008\IA32\SecMain.exe" /base:0x10000000 /pdb:"c:\edk2\Build\NT32\DEBUG_VS2008\IA32\SecMain.pdb" /LIBPATH:"C:\Program Files\Microsoft Visual Studio 9.0\VC\Lib" /LIBPATH:"C:\Program Files\Microsoft Visual Studio 9.0\VC\PlatformSdk\Lib" /NOLOGO /SUBSYSTEM:CONSOLE /NODEFAULTLIB /IGNORE:4086 /MAP /OPT:REF /DEBUG /MACHINE:I386 /LTCG Kernel32.lib MSVCRTD.lib Gdi32.lib User32.lib Winmm.lib Advapi32.lib /EXPORT:InitializeDriver=_ModuleEntryPoint /ALIGN:4096 /FILEALIGN:4096 /SUBSYSTEM:CONSOLE @c:\edk2\Build\NT32\DEBUG_VS2008\IA32\Nt32Pkg\Sec\SecMain\OUTPUT\static_library_files.lst
LINK : warning LNK4108: /ALIGN specified without /DRIVER; image may not run
LINK : warning LNK4001: no object files specified; libraries used
Creating library c:\edk2\Build\NT32\DEBUG_VS2008\IA32\SecMain.lib and object c:\edk2\Build\NT32\DEBUG_VS2008\IA32\SecMain.exp
Generating code
Finished generating code
"C:\Program Files\Microsoft Visual Studio 9.0\Vc\bin\link.exe" /OUT:c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\DEBUG\FloatTest.dll /NOLOGO /NODEFAULTLIB /IGNORE:4001 /OPT:REF /OPT:ICF=10 /MAP /ALIGN:32 /SECTION:.xdata,D /SECTION:.pdata,D /MACHINE:X86 /LTCG /DLL /ENTRY:_ModuleEntryPoint /SUBSYSTEM:EFI_BOOT_SERVICE_DRIVER /SAFESEH:NO /BASE:0 /DRIVER /DEBUG /EXPORT:InitializeDriver=_ModuleEntryPoint /ALIGN:4096 /FILEALIGN:4096 /SUBSYSTEM:CONSOLE @c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\OUTPUT\static_library_files.lst
Creating library c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\DEBUG\FloatTest.lib and object c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\DEBUG\FloatTest.exp
Generating code
Finished generating code
c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\DEBUG\FloatTest.dll : warning LNK4086: entrypoint '__ModuleEntryPoint' is not __stdcall with 12 bytes of arguments; image may not run
FloatTest.lib(floattest.obj) : error LNK2001: unresolved external symbol __fltused
c:\edk2\Build\NT32\DEBUG_VS2008\IA32\MdeModulePkg\Application\floattest\floattest\DEBUG\FloatTest.dll : fatal error LNK1120: 1 unresolved externals

我baidu和google之后得到的大概的结论是：UEFI 替换了Link中的默认库（CRT.LIB?），但是因为MS的编译器存在一个bug，所以导致仍然使用部分的默认库，所以导致这样的问题【这个解释存疑，不确定】。至于解决方法，经过我的实验确认就是使用 EADK 库【参考1】。我的理解是这个库是用来替代标准C库编写EDKII程序的，因此Float之类在其中也有重新定义。

加入方法：

1.解压EADK，然后将其中三个目录放到你EDK2的根目录下

2.修改 Nt32Pkg.dsc 加入红色部分

#
# Misc
#
DebugLib|IntelFrameworkModulePkg/Library/PeiDxeDebugLibReportStatusCode/PeiDxeDebugLibReportStatusCode.inf
DebugPrintErrorLevelLib|MdeModulePkg/Library/DxeDebugPrintErrorLevelLib/DxeDebugPrintErrorLevelLib.inf
PerformanceLib|MdePkg/Library/BasePerformanceLibNull/BasePerformanceLibNull.inf
DebugAgentLib|MdeModulePkg/Library/DebugAgentLibNull/DebugAgentLibNull.inf
#LABZ_Start
SortLib|ShellPkg/Library/UefiSortLib/UefiSortLib.inf
FileHandleLib|ShellPkg/Library/UefiFileHandleLib/UefiFileHandleLib.inf
ShellLib|ShellPkg/Library/UefiShellLib/UefiShellLib.inf
ShellCEntryLib|ShellPkg/Library/UefiShellCEntryLib/UefiShellCEntryLib.inf
LibC|StdLib/LibC/LibC.inf
LibStdLib|StdLib/LibC/StdLib/StdLib.inf
LibString|StdLib/LibC/String/String.inf
LibWchar|StdLib/LibC/Wchar/Wchar.inf
LibCType|StdLib/LibC/Ctype/Ctype.inf
LibTime|StdLib/LibC/Time/Time.inf
LibStdio|StdLib/LibC/Stdio/Stdio.inf
LibGdtoa|StdLib/LibC/gdtoa/gdtoa.inf
LibLocale|StdLib/LibC/Locale/Locale.inf
LibUefi|StdLib/LibC/Uefi/Uefi.inf
LibMath|StdLib/LibC/Math/Math.inf
LibSignal|StdLib/LibC/Signal/Signal.inf
LibNetUtil|StdLib/LibC/NetUtil/NetUtil.inf
#LABZ_End
[LibraryClasses.common.USER_DEFINED]
DebugLib|MdePkg/Library/BaseDebugLibNull/BaseDebugLibNull.inf
PeCoffExtraActionLib|MdePkg/Library/BasePeCoffExtraActionLibNull/BasePeCoffExtraActionLibNull.inf
ReportStatusCodeLib|MdeModulePkg/Library/PeiReportStatusCodeLib/PeiReportStatusCodeLib.inf
OemHookStatusCodeLib|Nt32Pkg/Library/PeiNt32OemHookStatusCodeLib/PeiNt32OemHookStatusCodeLib.inf
MemoryAllocationLib|MdePkg/Library/PeiMemoryAllocationLib/PeiMemoryAllocationLib.inf
PcdLib|MdePkg/Library/BasePcdLibNull/BasePcdLibNull.inf

3. floattest.inf 中必须加入下面2个

[LibraryClasses]
UefiApplicationEntryPoint
UefiLib
PcdLib
ShellCEntryLib
ShellLib
LibMath
LibC|

下面就可以在你的代码中放心大胆的使用Float了。

一个计算 Pi 的Shell Application

#include <Library/UefiLib.h>
#include <Library/ShellCEntryLib.h>

//
// Based on code found at http://code.google.com/p/my-itoa/
//
int 
Integer2AsciiString(int val, char* buf)
{
    const unsigned int radix = 10;

    char* p = buf;
    unsigned int a; 
    int len;
    char* b;
    char temp;
    unsigned int u;

    if (val < 0) {
        *p++ = '-';
        val = 0 - val;
    }
    u = (unsigned int)val;
    b = p;

    do {
        a = u % radix;
        u /= radix;
        *p++ =(char) a + '0';
    } while (u > 0);

    len = (int)(p - buf);
    *p-- = 0;

    // swap 
    do {
       temp = *p; *p = *b; *b = temp;
       --p; ++b;
    } while (b < p);

    return len;
}

//
// Based on code found on the Internet (author unknown)
// Search for ftoa implementations
//
int 
Float2AsciiString(float f, char *buffer, int numdecimals)
{
    int status = 0;
    char *s = buffer;
    long mantissa, int_part, frac_part;
    short exp2;
    char m;

    typedef union {
        long L;
        float F;
    } LF_t;
    LF_t x;

    if (f == 0.0) {           // return 0.00
        *s++ = '0'; *s++ = '.'; *s++ = '0'; *s++ = '0'; 
        *s = 0;
       return status;
    }

    x.F = f;

    exp2 = (unsigned char)(x.L >> 23) - 127;
    mantissa = (x.L & 0xFFFFFF) | 0x800000;
    frac_part = 0;
    int_part = 0;

    if (exp2 >= 31 || exp2 < -23) {
        *s = 0;
        return 1;
    } 

    if (exp2 >= 0) {
        int_part = mantissa >> (23 - exp2);
        frac_part = (mantissa << (exp2 + 1)) & 0xFFFFFF;
    } else {
        frac_part = (mantissa & 0xFFFFFF) >> -(exp2 + 1);
    }

    if (int_part == 0)
       *s++ = '0';
    else {
        Integer2AsciiString(int_part, s);
        while (*s) s++;
    }
    *s++ = '.';

    if (frac_part == 0)
        *s++ = '0';
    else {
        for (m = 0; m < numdecimals; m++) {                       // print BCD
            frac_part = (frac_part << 3) + (frac_part << 1);      // frac_part *= 10
            *s++ = (frac_part >> 24) + '0';
            frac_part &= 0xFFFFFF;
        }
    }
    *s = 0;

    return status;
}

VOID
Ascii2UnicodeString(CHAR8 *String, CHAR16 *UniString)
{
    while (*String != '\0') {
        *(UniString++) = (CHAR16) *(String++);
    }
    *UniString = '\0';
}

//PI= 4- /3+4/5-4/7+4/9
EFI_STATUS 
EFIAPI
CalcPI()
{
    char str[8];
    static CHAR16 wstr[8];
    int i;

    float g1 = (float) 1;
    float g2 = (float) 0;

    for (i=0;i<100;i++)
     {
	if (i%2==0) {g2=g2+ 4/ g1;}
        else {g2=g2-4/ g1;}
	Float2AsciiString(g2, str, 4);         
	Ascii2UnicodeString(str, wstr);
	Print(L" PI: %s\n", wstr);
        g1=g1+2;
     }

    return EFI_SUCCESS;
}

EFI_STATUS 
EFIAPI
UefiMain(EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
{

    CalcPI();

    return EFI_SUCCESS;
}

运行结果：

floattest

示例代码下载 floattest

参考：

1.http://sourceforge.net/apps/mediawiki/tianocore/index.php?title=EDKII_EADK

EDK II Application Development Kit for include the Standard C Libraries in UEFI Shell Applications

 

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