Table of Contents

GNU GENERAL PUBLIC LICENSE

Preamble
How to Apply These Terms to Your New Programs

Contributors to GNU Fortran
1. Funding Free Software
2. Funding GNU Fortran
3. Protect Your Freedom--Fight "Look And Feel"
4. Getting Started
5. What is GNU Fortran?
6. Compile Fortran, C, or Other Programs
7. GNU Fortran Command Options

7.1 Option Summary
7.2 Options Controlling the Kind of Output
7.3 Shorthand Options
7.4 Options Controlling Fortran Dialect
7.5 Options to Request or Suppress Warnings
7.6 Options for Debugging Your Program or GNU Fortran
7.7 Options That Control Optimization
7.8 Options Controlling the Preprocessor
7.9 Options for Directory Search
7.10 Options for Code Generation Conventions
7.11 Environment Variables Affecting GNU Fortran

8. News About GNU Fortran
9. User-visible Changes
10. The GNU Fortran Language

10.1 Direction of Language Development
10.2 ANSI FORTRAN 77 Standard Support

10.2.1 No Passing External Assumed-length
10.2.2 No Passing Dummy Assumed-length
10.2.3 No Pathological Implied-DO
10.2.4 No Useless Implied-DO

10.3 Conformance
10.4 Notation Used in This Chapter
10.5 Fortran Terms and Concepts

10.5.1 Syntactic Items
10.5.2 Statements, Comments, and Lines
10.5.3 Scope of Symbolic Names and Statement Labels

10.6 Characters, Lines, and Execution Sequence

10.6.1 GNU Fortran Character Set
10.6.2 Lines
10.6.3 Continuation Line
10.6.4 Statements
10.6.5 Statement Labels
10.6.6 Order of Statements and Lines
10.6.7 Including Source Text
10.6.8 Cpp-style directives

10.7 Data Types and Constants

10.7.1 Data Types

10.7.1.1 Double Notation
10.7.1.2 Star Notation
10.7.1.3 Kind Notation

10.7.2 Constants
10.7.3 Integer Type
10.7.4 Character Type

10.8 Expressions

10.8.1 The %LOC() Construct

10.9 Specification Statements

10.9.1 NAMELIST Statement
10.9.2 DOUBLE COMPLEX Statement

10.10 Control Statements

10.10.1 DO WHILE
10.10.2 END DO
10.10.3 Construct Names
10.10.4 The CYCLE and EXIT Statements

10.11 Functions and Subroutines

10.11.1 The %VAL() Construct
10.11.2 The %REF() Construct
10.11.3 The %DESCR() Construct
10.11.4 Generics and Specifics
10.11.5 REAL() and AIMAG() of Complex
10.11.6 CMPLX() of DOUBLE PRECISION
10.11.7 MIL-STD 1753 Support
10.11.8 f77/f2c Intrinsics
10.11.9 Table of Intrinsic Functions

10.11.9.1 Abort Intrinsic
10.11.9.2 Abs Intrinsic
10.11.9.3 Access Intrinsic
10.11.9.4 AChar Intrinsic
10.11.9.5 ACos Intrinsic
10.11.9.6 AdjustL Intrinsic
10.11.9.7 AdjustR Intrinsic
10.11.9.8 AImag Intrinsic
10.11.9.9 AInt Intrinsic
10.11.9.10 Alarm Intrinsic
10.11.9.11 All Intrinsic
10.11.9.12 Allocated Intrinsic
10.11.9.13 ALog Intrinsic
10.11.9.14 ALog10 Intrinsic
10.11.9.15 AMax0 Intrinsic
10.11.9.16 AMax1 Intrinsic
10.11.9.17 AMin0 Intrinsic
10.11.9.18 AMin1 Intrinsic
10.11.9.19 AMod Intrinsic
10.11.9.20 And Intrinsic
10.11.9.21 ANInt Intrinsic
10.11.9.22 Any Intrinsic
10.11.9.23 ASin Intrinsic
10.11.9.24 Associated Intrinsic
10.11.9.25 ATan Intrinsic
10.11.9.26 ATan2 Intrinsic
10.11.9.27 BesJ0 Intrinsic
10.11.9.28 BesJ1 Intrinsic
10.11.9.29 BesJN Intrinsic
10.11.9.30 BesY0 Intrinsic
10.11.9.31 BesY1 Intrinsic
10.11.9.32 BesYN Intrinsic
10.11.9.33 Bit_Size Intrinsic
10.11.9.34 BTest Intrinsic
10.11.9.35 CAbs Intrinsic
10.11.9.36 CCos Intrinsic
10.11.9.37 Ceiling Intrinsic
10.11.9.38 CExp Intrinsic
10.11.9.39 Char Intrinsic
10.11.9.40 ChDir Intrinsic (subroutine)
10.11.9.41 ChMod Intrinsic (subroutine)
10.11.9.42 CLog Intrinsic
10.11.9.43 Cmplx Intrinsic
10.11.9.44 Complex Intrinsic
10.11.9.45 Conjg Intrinsic
10.11.9.46 Cos Intrinsic
10.11.9.47 CosH Intrinsic
10.11.9.48 Count Intrinsic
10.11.9.49 CPU_Time Intrinsic
10.11.9.50 CShift Intrinsic
10.11.9.51 CSin Intrinsic
10.11.9.52 CSqRt Intrinsic
10.11.9.53 CTime Intrinsic (subroutine)
10.11.9.54 CTime Intrinsic (function)
10.11.9.55 DAbs Intrinsic
10.11.9.56 DACos Intrinsic
10.11.9.57 DASin Intrinsic
10.11.9.58 DATan Intrinsic
10.11.9.59 DATan2 Intrinsic
10.11.9.60 Date_and_Time Intrinsic
10.11.9.61 DbesJ0 Intrinsic
10.11.9.62 DbesJ1 Intrinsic
10.11.9.63 DbesJN Intrinsic
10.11.9.64 DbesY0 Intrinsic
10.11.9.65 DbesY1 Intrinsic
10.11.9.66 DbesYN Intrinsic
10.11.9.67 Dble Intrinsic
10.11.9.68 DCos Intrinsic
10.11.9.69 DCosH Intrinsic
10.11.9.70 DDiM Intrinsic
10.11.9.71 DErF Intrinsic
10.11.9.72 DErFC Intrinsic
10.11.9.73 DExp Intrinsic
10.11.9.74 Digits Intrinsic
10.11.9.75 DiM Intrinsic
10.11.9.76 DInt Intrinsic
10.11.9.77 DLog Intrinsic
10.11.9.78 DLog10 Intrinsic
10.11.9.79 DMax1 Intrinsic
10.11.9.80 DMin1 Intrinsic
10.11.9.81 DMod Intrinsic
10.11.9.82 DNInt Intrinsic
10.11.9.83 Dot_Product Intrinsic
10.11.9.84 DProd Intrinsic
10.11.9.85 DSign Intrinsic
10.11.9.86 DSin Intrinsic
10.11.9.87 DSinH Intrinsic
10.11.9.88 DSqRt Intrinsic
10.11.9.89 DTan Intrinsic
10.11.9.90 DTanH Intrinsic
10.11.9.91 DTime Intrinsic (subroutine)
10.11.9.92 EOShift Intrinsic
10.11.9.93 Epsilon Intrinsic
10.11.9.94 ErF Intrinsic
10.11.9.95 ErFC Intrinsic
10.11.9.96 ETime Intrinsic (subroutine)
10.11.9.97 ETime Intrinsic (function)
10.11.9.98 Exit Intrinsic
10.11.9.99 Exp Intrinsic
10.11.9.100 Exponent Intrinsic
10.11.9.101 FDate Intrinsic (subroutine)
10.11.9.102 FDate Intrinsic (function)
10.11.9.103 FGet Intrinsic (subroutine)
10.11.9.104 FGetC Intrinsic (subroutine)
10.11.9.105 Float Intrinsic
10.11.9.106 Floor Intrinsic
10.11.9.107 Flush Intrinsic
10.11.9.108 FNum Intrinsic
10.11.9.109 FPut Intrinsic (subroutine)
10.11.9.110 FPutC Intrinsic (subroutine)
10.11.9.111 Fraction Intrinsic
10.11.9.112 FSeek Intrinsic
10.11.9.113 FStat Intrinsic (subroutine)
10.11.9.114 FStat Intrinsic (function)
10.11.9.115 FTell Intrinsic (subroutine)
10.11.9.116 FTell Intrinsic (function)
10.11.9.117 GError Intrinsic
10.11.9.118 GetArg Intrinsic
10.11.9.119 GetCWD Intrinsic (subroutine)
10.11.9.120 GetCWD Intrinsic (function)
10.11.9.121 GetEnv Intrinsic
10.11.9.122 GetGId Intrinsic
10.11.9.123 GetLog Intrinsic
10.11.9.124 GetPId Intrinsic
10.11.9.125 GetUId Intrinsic
10.11.9.126 GMTime Intrinsic
10.11.9.127 HostNm Intrinsic (subroutine)
10.11.9.128 HostNm Intrinsic (function)
10.11.9.129 Huge Intrinsic
10.11.9.130 IAbs Intrinsic
10.11.9.131 IAChar Intrinsic
10.11.9.132 IAnd Intrinsic
10.11.9.133 IArgC Intrinsic
10.11.9.134 IBClr Intrinsic
10.11.9.135 IBits Intrinsic
10.11.9.136 IBSet Intrinsic
10.11.9.137 IChar Intrinsic
10.11.9.138 IDate Intrinsic (UNIX)
10.11.9.139 IDiM Intrinsic
10.11.9.140 IDInt Intrinsic
10.11.9.141 IDNInt Intrinsic
10.11.9.142 IEOr Intrinsic
10.11.9.143 IErrNo Intrinsic
10.11.9.144 IFix Intrinsic
10.11.9.145 Imag Intrinsic
10.11.9.146 ImagPart Intrinsic
10.11.9.147 Index Intrinsic
10.11.9.148 Int Intrinsic
10.11.9.149 Int2 Intrinsic
10.11.9.150 Int8 Intrinsic
10.11.9.151 IOr Intrinsic
10.11.9.152 IRand Intrinsic
10.11.9.153 IsaTty Intrinsic
10.11.9.154 IShft Intrinsic
10.11.9.155 IShftC Intrinsic
10.11.9.156 ISign Intrinsic
10.11.9.157 ITime Intrinsic
10.11.9.158 Kill Intrinsic (subroutine)
10.11.9.159 Kind Intrinsic
10.11.9.160 LBound Intrinsic
10.11.9.161 Len Intrinsic
10.11.9.162 Len_Trim Intrinsic
10.11.9.163 LGe Intrinsic
10.11.9.164 LGt Intrinsic
10.11.9.165 Link Intrinsic (subroutine)
10.11.9.166 LLe Intrinsic
10.11.9.167 LLt Intrinsic
10.11.9.168 LnBlnk Intrinsic
10.11.9.169 Loc Intrinsic
10.11.9.170 Log Intrinsic
10.11.9.171 Log10 Intrinsic
10.11.9.172 Logical Intrinsic
10.11.9.173 Long Intrinsic
10.11.9.174 LShift Intrinsic
10.11.9.175 LStat Intrinsic (subroutine)
10.11.9.176 LStat Intrinsic (function)
10.11.9.177 LTime Intrinsic
10.11.9.178 MatMul Intrinsic
10.11.9.179 Max Intrinsic
10.11.9.180 Max0 Intrinsic
10.11.9.181 Max1 Intrinsic
10.11.9.182 MaxExponent Intrinsic
10.11.9.183 MaxLoc Intrinsic
10.11.9.184 MaxVal Intrinsic
10.11.9.185 MClock Intrinsic
10.11.9.186 MClock8 Intrinsic
10.11.9.187 Merge Intrinsic
10.11.9.188 Min Intrinsic
10.11.9.189 Min0 Intrinsic
10.11.9.190 Min1 Intrinsic
10.11.9.191 MinExponent Intrinsic
10.11.9.192 MinLoc Intrinsic
10.11.9.193 MinVal Intrinsic
10.11.9.194 Mod Intrinsic
10.11.9.195 Modulo Intrinsic
10.11.9.196 MvBits Intrinsic
10.11.9.197 Nearest Intrinsic
10.11.9.198 NInt Intrinsic
10.11.9.199 Not Intrinsic
10.11.9.200 Or Intrinsic
10.11.9.201 Pack Intrinsic
10.11.9.202 PError Intrinsic
10.11.9.203 Precision Intrinsic
10.11.9.204 Present Intrinsic
10.11.9.205 Product Intrinsic
10.11.9.206 Radix Intrinsic
10.11.9.207 Rand Intrinsic
10.11.9.208 Random_Number Intrinsic
10.11.9.209 Random_Seed Intrinsic
10.11.9.210 Range Intrinsic
10.11.9.211 Real Intrinsic
10.11.9.212 RealPart Intrinsic
10.11.9.213 Rename Intrinsic (subroutine)
10.11.9.214 Repeat Intrinsic
10.11.9.215 Reshape Intrinsic
10.11.9.216 RRSpacing Intrinsic
10.11.9.217 RShift Intrinsic
10.11.9.218 Scale Intrinsic
10.11.9.219 Scan Intrinsic
10.11.9.220 Second Intrinsic (function)
10.11.9.221 Second Intrinsic (subroutine)
10.11.9.222 Selected_Int_Kind Intrinsic
10.11.9.223 Selected_Real_Kind Intrinsic
10.11.9.224 Set_Exponent Intrinsic
10.11.9.225 Shape Intrinsic
10.11.9.226 Short Intrinsic
10.11.9.227 Sign Intrinsic
10.11.9.228 Signal Intrinsic (subroutine)
10.11.9.229 Sin Intrinsic
10.11.9.230 SinH Intrinsic
10.11.9.231 Sleep Intrinsic
10.11.9.232 Sngl Intrinsic
10.11.9.233 Spacing Intrinsic
10.11.9.234 Spread Intrinsic
10.11.9.235 SqRt Intrinsic
10.11.9.236 SRand Intrinsic
10.11.9.237 Stat Intrinsic (subroutine)
10.11.9.238 Stat Intrinsic (function)
10.11.9.239 Sum Intrinsic
10.11.9.240 SymLnk Intrinsic (subroutine)
10.11.9.241 System Intrinsic (subroutine)
10.11.9.242 System_Clock Intrinsic
10.11.9.243 Tan Intrinsic
10.11.9.244 TanH Intrinsic
10.11.9.245 Time Intrinsic (UNIX)
10.11.9.246 Time8 Intrinsic
10.11.9.247 Tiny Intrinsic
10.11.9.248 Transfer Intrinsic
10.11.9.249 Transpose Intrinsic
10.11.9.250 Trim Intrinsic
10.11.9.251 TtyNam Intrinsic (subroutine)
10.11.9.252 TtyNam Intrinsic (function)
10.11.9.253 UBound Intrinsic
10.11.9.254 UMask Intrinsic (subroutine)
10.11.9.255 Unlink Intrinsic (subroutine)
10.11.9.256 Unpack Intrinsic
10.11.9.257 Verify Intrinsic
10.11.9.258 XOr Intrinsic
10.11.9.259 ZAbs Intrinsic
10.11.9.260 ZCos Intrinsic
10.11.9.261 ZExp Intrinsic
10.11.9.262 ZLog Intrinsic
10.11.9.263 ZSin Intrinsic
10.11.9.264 ZSqRt Intrinsic

10.12 Scope and Classes of Symbolic Names

10.12.1 Underscores in Symbol Names

10.13 I/O
10.14 Fortran 90 Features

11. Other Dialects

11.1 Source Form

11.1.1 Carriage Returns
11.1.2 Tabs
11.1.3 Short Lines
11.1.4 Long Lines
11.1.5 Ampersand Continuation Line

11.2 Trailing Comment
11.3 Debug Line
11.4 Dollar Signs in Symbol Names
11.5 Case Sensitivity
11.6 VXT Fortran

11.6.1 Meaning of Double Quote
11.6.2 Meaning of Exclamation Point in Column 6

11.7 Fortran 90
11.8 Pedantic Compilation
11.9 Distensions

11.9.1 Implicit Argument Conversion
11.9.2 Ugly Assumed-Size Arrays
11.9.3 Ugly Complex Part Extraction
11.9.4 Ugly Null Arguments
11.9.5 Ugly Conversion of Initializers
11.9.6 Ugly Integer Conversions
11.9.7 Ugly Assigned Labels

12. The GNU Fortran Compiler

12.1 Compiler Limits
12.2 Run-time Environment Limits

12.2.1 Timer Wraparounds
12.2.2 Year 2000 (Y2K) Problems
12.2.3 Array Size
12.2.4 Character-variable Length
12.2.5 Year 10000 (Y10K) Problems

12.3 Compiler Types
12.4 Compiler Constants
12.5 Compiler Intrinsics

12.5.1 Intrinsic Groups
12.5.2 Other Intrinsics

12.5.2.1 ACosD Intrinsic
12.5.2.2 AIMax0 Intrinsic
12.5.2.3 AIMin0 Intrinsic
12.5.2.4 AJMax0 Intrinsic
12.5.2.5 AJMin0 Intrinsic
12.5.2.6 ASinD Intrinsic
12.5.2.7 ATan2D Intrinsic
12.5.2.8 ATanD Intrinsic
12.5.2.9 BITest Intrinsic
12.5.2.10 BJTest Intrinsic
12.5.2.11 CDAbs Intrinsic
12.5.2.12 CDCos Intrinsic
12.5.2.13 CDExp Intrinsic
12.5.2.14 CDLog Intrinsic
12.5.2.15 CDSin Intrinsic
12.5.2.16 CDSqRt Intrinsic
12.5.2.17 ChDir Intrinsic (function)
12.5.2.18 ChMod Intrinsic (function)
12.5.2.19 CosD Intrinsic
12.5.2.20 DACosD Intrinsic
12.5.2.21 DASinD Intrinsic
12.5.2.22 DATan2D Intrinsic
12.5.2.23 DATanD Intrinsic
12.5.2.24 Date Intrinsic
12.5.2.25 DbleQ Intrinsic
12.5.2.26 DCmplx Intrinsic
12.5.2.27 DConjg Intrinsic
12.5.2.28 DCosD Intrinsic
12.5.2.29 DFloat Intrinsic
12.5.2.30 DFlotI Intrinsic
12.5.2.31 DFlotJ Intrinsic
12.5.2.32 DImag Intrinsic
12.5.2.33 DReal Intrinsic
12.5.2.34 DSinD Intrinsic
12.5.2.35 DTanD Intrinsic
12.5.2.36 DTime Intrinsic (function)
12.5.2.37 FGet Intrinsic (function)
12.5.2.38 FGetC Intrinsic (function)
12.5.2.39 FloatI Intrinsic
12.5.2.40 FloatJ Intrinsic
12.5.2.41 FPut Intrinsic (function)
12.5.2.42 FPutC Intrinsic (function)
12.5.2.43 IDate Intrinsic (VXT)
12.5.2.44 IIAbs Intrinsic
12.5.2.45 IIAnd Intrinsic
12.5.2.46 IIBClr Intrinsic
12.5.2.47 IIBits Intrinsic
12.5.2.48 IIBSet Intrinsic
12.5.2.49 IIDiM Intrinsic
12.5.2.50 IIDInt Intrinsic
12.5.2.51 IIDNnt Intrinsic
12.5.2.52 IIEOr Intrinsic
12.5.2.53 IIFix Intrinsic
12.5.2.54 IInt Intrinsic
12.5.2.55 IIOr Intrinsic
12.5.2.56 IIQint Intrinsic
12.5.2.57 IIQNnt Intrinsic
12.5.2.58 IIShftC Intrinsic
12.5.2.59 IISign Intrinsic
12.5.2.60 IMax0 Intrinsic
12.5.2.61 IMax1 Intrinsic
12.5.2.62 IMin0 Intrinsic
12.5.2.63 IMin1 Intrinsic
12.5.2.64 IMod Intrinsic
12.5.2.65 INInt Intrinsic
12.5.2.66 INot Intrinsic
12.5.2.67 IZExt Intrinsic
12.5.2.68 JIAbs Intrinsic
12.5.2.69 JIAnd Intrinsic
12.5.2.70 JIBClr Intrinsic
12.5.2.71 JIBits Intrinsic
12.5.2.72 JIBSet Intrinsic
12.5.2.73 JIDiM Intrinsic
12.5.2.74 JIDInt Intrinsic
12.5.2.75 JIDNnt Intrinsic
12.5.2.76 JIEOr Intrinsic
12.5.2.77 JIFix Intrinsic
12.5.2.78 JInt Intrinsic
12.5.2.79 JIOr Intrinsic
12.5.2.80 JIQint Intrinsic
12.5.2.81 JIQNnt Intrinsic
12.5.2.82 JIShft Intrinsic
12.5.2.83 JIShftC Intrinsic
12.5.2.84 JISign Intrinsic
12.5.2.85 JMax0 Intrinsic
12.5.2.86 JMax1 Intrinsic
12.5.2.87 JMin0 Intrinsic
12.5.2.88 JMin1 Intrinsic
12.5.2.89 JMod Intrinsic
12.5.2.90 JNInt Intrinsic
12.5.2.91 JNot Intrinsic
12.5.2.92 JZExt Intrinsic
12.5.2.93 Kill Intrinsic (function)
12.5.2.94 Link Intrinsic (function)
12.5.2.95 QAbs Intrinsic
12.5.2.96 QACos Intrinsic
12.5.2.97 QACosD Intrinsic
12.5.2.98 QASin Intrinsic
12.5.2.99 QASinD Intrinsic
12.5.2.100 QATan Intrinsic
12.5.2.101 QATan2 Intrinsic
12.5.2.102 QATan2D Intrinsic
12.5.2.103 QATanD Intrinsic
12.5.2.104 QCos Intrinsic
12.5.2.105 QCosD Intrinsic
12.5.2.106 QCosH Intrinsic
12.5.2.107 QDiM Intrinsic
12.5.2.108 QExp Intrinsic
12.5.2.109 QExt Intrinsic
12.5.2.110 QExtD Intrinsic
12.5.2.111 QFloat Intrinsic
12.5.2.112 QInt Intrinsic
12.5.2.113 QLog Intrinsic
12.5.2.114 QLog10 Intrinsic
12.5.2.115 QMax1 Intrinsic
12.5.2.116 QMin1 Intrinsic
12.5.2.117 QMod Intrinsic
12.5.2.118 QNInt Intrinsic
12.5.2.119 QSin Intrinsic
12.5.2.120 QSinD Intrinsic
12.5.2.121 QSinH Intrinsic
12.5.2.122 QSqRt Intrinsic
12.5.2.123 QTan Intrinsic
12.5.2.124 QTanD Intrinsic
12.5.2.125 QTanH Intrinsic
12.5.2.126 Rename Intrinsic (function)
12.5.2.127 Secnds Intrinsic
12.5.2.128 Signal Intrinsic (function)
12.5.2.129 SinD Intrinsic
12.5.2.130 SnglQ Intrinsic
12.5.2.131 SymLnk Intrinsic (function)
12.5.2.132 System Intrinsic (function)
12.5.2.133 TanD Intrinsic
12.5.2.134 Time Intrinsic (VXT)
12.5.2.135 UMask Intrinsic (function)
12.5.2.136 Unlink Intrinsic (function)
12.5.2.137 ZExt Intrinsic

13. Other Compilers

13.1 Dropping f2c Compatibility
13.2 Compilers Other Than f2c

14. Other Languages

14.1 Tools and advice for interoperating with C and C++

14.1.1 C Interfacing Tools
14.1.2 Accessing Type Information in C
14.1.3 Generating Skeletons and Prototypes with f2c
14.1.4 C++ Considerations
14.1.5 Startup Code

15. Installing GNU Fortran

15.1 Prerequisites
15.2 Problems Installing

15.2.1 General Problems

15.2.1.1 GNU C Required
15.2.1.2 Patching GNU CC
15.2.1.3 Building GNU CC Necessary
15.2.1.4 Missing strtoul or bsearch
15.2.1.5 Cleanup Kills Stage Directories
15.2.1.6 LANGUAGES Macro Ignored

15.2.2 System-specific Problems
15.2.3 Cross-compiler Problems

15.3 Changing Settings Before Building

15.3.1 Larger File Unit Numbers
15.3.2 Always Flush Output
15.3.3 Maximum Stackable Size
15.3.4 Floating-point Bit Patterns
15.3.5 Initialization of Large Aggregate Areas
15.3.6 Alpha Problems Fixed

15.4 Quick Start
15.5 Complete Installation
15.6 Distributing Binaries

16. Debugging and Interfacing

16.1 Main Program Unit (PROGRAM)
16.2 Procedures (SUBROUTINE and FUNCTION)
16.3 Functions (FUNCTION and RETURN)
16.4 Names
16.5 Common Blocks (COMMON)
16.6 Local Equivalence Areas (EQUIVALENCE)
16.7 Complex Variables (COMPLEX)
16.8 Arrays (DIMENSION)
16.9 Adjustable Arrays (DIMENSION)
16.10 Alternate Entry Points (ENTRY)
16.11 Alternate Returns (SUBROUTINE and RETURN)
16.12 Assigned Statement Labels (ASSIGN and GOTO)
16.13 Run-time Library Errors

17. Collected Fortran Wisdom

17.1 Advantages Over f2c

17.1.1 Language Extensions
17.1.2 Diagnostic Abilities
17.1.3 Compiler Options
17.1.4 Compiler Speed
17.1.5 Program Speed
17.1.6 Ease of Debugging
17.1.7 Character and Hollerith Constants

17.2 Block Data and Libraries
17.3 Loops
17.4 Working Programs

17.4.1 Not My Type
17.4.2 Variables Assumed To Be Zero
17.4.3 Variables Assumed To Be Saved
17.4.4 Unwanted Variables
17.4.5 Unused Arguments
17.4.6 Surprising Interpretations of Code
17.4.7 Aliasing Assumed To Work
17.4.8 Output Assumed To Flush
17.4.9 Large File Unit Numbers
17.4.10 Floating-point precision
17.4.11 Inconsistent Calling Sequences

17.5 Overly Convenient Command-line Options
17.6 Faster Programs

17.6.1 Aligned Data
17.6.2 Prefer Automatic Uninitialized Variables
17.6.3 Avoid f2c Compatibility
17.6.4 Use Submodel Options

18. Known Causes of Trouble with GNU Fortran

18.1 Bugs Not In GNU Fortran

18.1.1 Signal 11 and Friends
18.1.2 Cannot Link Fortran Programs
18.1.3 Large Common Blocks
18.1.4 Debugger Problems
18.1.5 NeXTStep Problems
18.1.6 Stack Overflow
18.1.7 Nothing Happens
18.1.8 Strange Behavior at Run Time
18.1.9 Floating-point Errors

18.2 Known Bugs In GNU Fortran
18.3 Missing Features

18.3.1 Better Source Model
18.3.2 Fortran 90 Support
18.3.3 Intrinsics in PARAMETER Statements
18.3.4 Arbitrary Concatenation
18.3.5 SELECT CASE on CHARACTER Type
18.3.6 RECURSIVE Keyword
18.3.7 Increasing Precision/Range
18.3.8 Popular Non-standard Types
18.3.9 Full Support for Compiler Types
18.3.10 Array Bounds Expressions
18.3.11 POINTER Statements
18.3.12 Sensible Non-standard Constructs
18.3.13 READONLY Keyword
18.3.14 FLUSH Statement
18.3.15 Expressions in FORMAT Statements
18.3.16 Explicit Assembler Code
18.3.17 Q Edit Descriptor
18.3.18 Old-style PARAMETER Statements
18.3.19 TYPE and ACCEPT I/O Statements
18.3.20 STRUCTURE, UNION, RECORD, MAP
18.3.21 OPEN, CLOSE, and INQUIRE Keywords
18.3.22 ENCODE and DECODE
18.3.23 AUTOMATIC Statement
18.3.24 Suppressing Space Padding of Source Lines
18.3.25 Fortran Preprocessor
18.3.26 Bit Operations on Floating-point Data
18.3.27 Really Ugly Character Assignments
18.3.28 POSIX Standard
18.3.29 Floating-point Exception Handling
18.3.30 Nonportable Conversions
18.3.31 Large Automatic Arrays
18.3.32 Support for Threads
18.3.33 Enabling Debug Lines
18.3.34 Better Warnings
18.3.35 Gracefully Handle Sensible Bad Code
18.3.36 Non-standard Conversions
18.3.37 Non-standard Intrinsics
18.3.38 Modifying DO Variable
18.3.39 Better Pedantic Compilation
18.3.40 Warn About Implicit Conversions
18.3.41 Invalid Use of Hollerith Constant
18.3.42 Dummy Array Without Dimensioning Dummy
18.3.43 Invalid FORMAT Specifiers
18.3.44 Ambiguous Dialects
18.3.45 Unused Labels
18.3.46 Informational Messages
18.3.47 Uninitialized Variables at Run Time
18.3.48 Portable Unformatted Files
18.3.49 Better List-directed I/O
18.3.50 Default to Console I/O
18.3.51 Labels Visible to Debugger

18.4 Disappointments and Misunderstandings

18.4.1 Mangling of Names in Source Code
18.4.2 Multiple Definitions of External Names
18.4.3 Limitation on Implicit Declarations

18.5 Certain Changes We Don't Want to Make

18.5.1 Backslash in Constants
18.5.2 Initializing Before Specifying
18.5.3 Context-Sensitive Intrinsicness
18.5.4 Context-Sensitive Constants
18.5.5 Equivalence Versus Equality
18.5.6 Order of Side Effects

18.6 Warning Messages and Error Messages

19. Open Questions
20. Reporting Bugs

20.1 Have You Found a Bug?
20.2 Where to Report Bugs
20.3 How to Report Bugs
20.4 Sending Patches for GNU Fortran

21. How To Get Help with GNU Fortran
22. Adding Options
23. Projects

23.1 Improve Efficiency
23.2 Better Optimization
23.3 Simplify Porting
23.4 More Extensions
23.5 Machine Model
23.6 Internals Documentation
23.7 Internals Improvements
23.8 Better Diagnostics

24. Front End

24.1 Overview of Sources
24.2 Overview of Translation Process

24.2.1 g77stripcard
24.2.2 lex.c
24.2.3 sta.c
24.2.4 stb.c
24.2.5 expr.c
24.2.6 stc.c
24.2.7 std.c
24.2.8 ste.c
24.2.9 Gotchas (Transforming)

24.2.9.1 Multi-character Lexemes
24.2.9.2 Space-padding Lexemes
24.2.9.3 Bizarre Free-form Hollerith Constants
24.2.9.4 Hollerith Constants
24.2.9.5 Confusing Function Keyword
24.2.9.6 Weird READ

24.2.10 TBD (Transforming)

24.3 Philosophy of Code Generation
24.4 Two-pass Design

24.4.1 Two-pass Code
24.4.2 Why Two Passes

24.5 Challenges Posed
24.6 Transforming Statements

24.6.1 Statements Needing Temporaries
24.6.2 Transforming DO WHILE
24.6.3 Transforming Iterative DO
24.6.4 Transforming Block IF
24.6.5 Transforming SELECT CASE

24.7 Transforming Expressions
24.8 Internal Naming Conventions

25. Diagnostics

25.1 CMPAMBIG
25.2 EXPIMP
25.3 INTGLOB
25.4 LEX
25.5 GLOBALS
25.6 LINKFAIL
25.7 Y2KBAD

Index