diff options
author | kargl <kargl@138bc75d-0d04-0410-961f-82ee72b054a4> | 2016-05-14 16:00:35 +0000 |
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committer | kargl <kargl@138bc75d-0d04-0410-961f-82ee72b054a4> | 2016-05-14 16:00:35 +0000 |
commit | a5f52592ba06736fddfe47d3fc8c0e676f11fa5d (patch) | |
tree | 273671f57d952a072a77b50672efbedfcb3ebc7c /gcc/fortran/gfortran.texi | |
parent | 88f949ab2dfe37d9da82648018fa609f1d5a1520 (diff) |
2016-05-14 Fritz Reese <fritzoreese@gmail.com>
* gfortran.dg/dec_union_4.f90: Fix endian issue.
2016-05-14 Fritz Reese <fritzoreese@gmail.com>
* gfortran.texi: Update example of DEC UNION extension.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@236242 138bc75d-0d04-0410-961f-82ee72b054a4
Diffstat (limited to 'gcc/fortran/gfortran.texi')
-rw-r--r-- | gcc/fortran/gfortran.texi | 77 |
1 files changed, 35 insertions, 42 deletions
diff --git a/gcc/fortran/gfortran.texi b/gcc/fortran/gfortran.texi index 9d7d3d4b34b..4d288bafac3 100644 --- a/gcc/fortran/gfortran.texi +++ b/gcc/fortran/gfortran.texi @@ -2281,28 +2281,25 @@ Here is a small example: structure /myunion/ union map - integer(2) w, x, y, z + character(2) w0, w1, w2 end map map - integer(4) wx, yz + character(6) long end map end union end structure record /myunion/ rec -! After these assignments... -rec.wx = z'0DEDBEEF' -rec.y = z'0BAD' -rec.z = z'0FAD' +! After this assignment... +rec.long = 'hello!' ! The following is true: -! rec.w === z'0DED' -! rec.x === z'BEEF' -! rec.yz === z'0BAD0FAD' +! rec.w0 === 'he' +! rec.w1 === 'll' +! rec.w2 === 'o!' @end smallexample -The two maps share memory, and the size of the union is ultimately six bytes -(subject to alignment): +The two maps share memory, and the size of the union is ultimately six bytes: @example 0 1 2 3 4 5 6 Byte offset @@ -2313,65 +2310,61 @@ The two maps share memory, and the size of the union is ultimately six bytes ^ W0 ^ W1 ^ W2 ^ \-------/ \-------/ \-------/ -^ LONG ^ unused ^ - \-----------------/ \-------/ +^ LONG ^ + \---------------------------/ @end example Following is an example mirroring the layout of an Intel x86_64 register: @example structure /reg/ - union ! rax + union ! U0 ! rax map - integer*8 rx ! rax + character(16) rx end map map - integer*4 rh ! rah - union ! eax + character(8) rh ! rah + union ! U1 map - integer*4 rl ! ral + character(8) rl ! ral end map map - integer*4 ex ! eax + character(8) ex ! eax end map map - integer*2 eh ! eah - union ! ax + character(4) eh ! eah + union ! U2 map - integer*2 el ! eal + character(4) el ! eal end map map - integer*2 x ! ax + character(4) x ! ax end map map - integer*1 h ! ah - integer*1 l ! al + character(2) h ! ah + character(2) l ! al end map - end union ! ax + end union end map - end union ! eax + end union end map - end union ! rax + end union end structure - record /reg/ a ! After this assignment... -a.rx = z'AABBCCCCFFFFFFFF' +a.rx = 'AAAAAAAA.BBB.C.D' ! The following is true: -! -! a.rx == z'AABBCCCCFFFFFFFF' -! a.rh == z'FFFFFFFF' -! a.rl == z'AABBCCCC' -! -! a.ex == z'AABBCCCC' -! a.eh == z'CCCC' -! a.el == z'AABB' -! -! a.x == z'AABB' -! a.h == z'BB' -! a.l == z'AA' +a.rx === 'AAAAAAAA.BBB.C.D' +a.rh === 'AAAAAAAA' +a.rl === '.BBB.C.D' +a.ex === '.BBB.C.D' +a.eh === '.BBB' +a.el === '.C.D' +a.x === '.C.D' +a.h === '.C' +a.l === '.D' @end example |