[解决]编译 webkitgtk-2.18.6 有个奇怪的问题。是架构的特殊问题，还是 python 的浮点计算出错？

解决，gcc 的 rpm 在 configure 时增加了 --with-madd4=no 。
在重新编译 glibc ，之后重编译 python2 就好了。
==========
请注意，有些内容被吞了，比如
print ".16f"%memoryBits
其实应该是
print "％16.16f"%memoryBits
第一个百分号，替换成了汉字全角才现实。
-------------------------------------------

--- webkitgtk-2.18.6-orig/Source/JavaScriptCore/wasm/generateWasm.py    2018-03-03 19:01:28.441007606 +0800

+++ webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasm.py 2018-03-03 19:03:56.015243319 +0800

@@ -101,5 +101,5 @@

     assert op["opcode"]["category"] == "memory"

     match = re.match(r'^[if]([36][24])\.[^0-9]+([0-9]+)?_?[us]?$', op["name"])

     memoryBits = int(match.group(2) if match.group(2) else match.group(1))

-    assert 2 ** math.log(memoryBits, 2) == memoryBits

+    assert 2 ** int(math.log(memoryBits, 2)) == memoryBits

     return str(int(math.log(memoryBits / 8, 2)))

这个 patch 这么打就可以编译过，不然 assert 这里 == 的前面不是一个整数，导致前后不相等而报错退出。

把这里修改一下，输出这些数据：

def memoryLog2Alignment(op):

    assert op["opcode"]["category"] == "memory"

    match = re.match(r'^[if]([36][24])\.[^0-9]+([0-9]+)?_?[us]?$', op["name"])

    memoryBits = int(match.group(2) if match.group(2) else match.group(1))

    print "data:"

    print memoryBits

    print math.log(memoryBits, 2)

    print 2 ** math.log(memoryBits, 2)

    print "-----"

    assert 2 ** math.log(memoryBits, 2) == memoryBits

    return str(int(math.log(memoryBits / 8, 2)))

输出如下。也就是说，其实两个数一样，顶多一个是整数，一个是浮点。但是就是不相等？

cd /builddir/build/BUILD/webkitgtk-2.18.6/mips64el-redhat-linux-gnu/Source/JavaScriptCore && /usr/bin/python2.7 /builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py /builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/wasm.json /builddir/build/BUILD/webkitgtk-2.18.6/mips64el-redhat-linux-gnu/DerivedSources/JavaScriptCore/WasmOps.h

data:

32

5.0

32.0

-----

data:

32

5.0

32.0

-----

data:

16

4.0

16.0

-----

data:

16

4.0

16.0

-----

data:

64

6.0

64.0

-----

Traceback (most recent call last):

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py", line 115, in <module>

    memoryLog2AlignmentLoads = memoryLog2AlignmentGenerator(lambda op: (op["category"] == "memory" and len(op["return"]) == 1))

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py", line 112, in memoryLog2AlignmentGenerator

    result.append("    case " + wasm.toCpp(op["name"]) + ": return " + memoryLog2Alignment(op) + ";")

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasm.py", line 109, in memoryLog2Alignment

    assert 2 ** math.log(memoryBits, 2) == memoryBits

AssertionError

设定输出为浮点数：

def memoryLog2Alignment(op):

    assert op["opcode"]["category"] == "memory"

    match = re.match(r'^[if]([36][24])\.[^0-9]+([0-9]+)?_?[us]?$', op["name"])

    memoryBits = int(match.group(2) if match.group(2) else match.group(1))

    print "data:"

    print ".16f"%memoryBits

    print ".16f"%math.log(memoryBits, 2)

    print ".16f"%(2 ** math.log(memoryBits, 2))

    print "-----"

    assert 2 ** math.log(memoryBits, 2) == memoryBits

    return str(int(math.log(memoryBits / 8, 2)))

终于暴露目标了

cd /builddir/build/BUILD/webkitgtk-2.18.6/mips64el-redhat-linux-gnu/Source/JavaScriptCore && /usr/bin/python2.7 /builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py /builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/wasm.json /builddir/build/BUILD/webkitgtk-2.18.6/mips64el-redhat-linux-gnu/DerivedSources/JavaScriptCore/WasmOps.h

data:

32.0000000000000000

5.0000000000000000

32.0000000000000000

-----

data:

32.0000000000000000

5.0000000000000000

32.0000000000000000

-----

data:

16.0000000000000000

4.0000000000000000

16.0000000000000000

-----

data:

16.0000000000000000

4.0000000000000000

16.0000000000000000

-----

data:

64.0000000000000000

6.0000000000000000

63.9999999999999858

-----

Traceback (most recent call last):

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py", line 115, in <module>

    memoryLog2AlignmentLoads = memoryLog2AlignmentGenerator(lambda op: (op["category"] == "memory" and len(op["return"]) == 1))

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasmOpsHeader.py", line 112, in memoryLog2AlignmentGenerator

    result.append("    case " + wasm.toCpp(op["name"]) + ": return " + memoryLog2Alignment(op) + ";")

  File "/builddir/build/BUILD/webkitgtk-2.18.6/Source/JavaScriptCore/wasm/generateWasm.py", line 109, in memoryLog2Alignment

    assert 2 ** math.log(memoryBits, 2) == memoryBits

AssertionError

浮点计算错！