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Using and Porting GNU Fortran

Table of Contents

GNU GENERAL PUBLIC LICENSE

Preamble
How to Apply These Terms to Your New Programs

GNU Free Documentation License

ADDENDUM: How to use this License for your documents

Contributors to GNU Fortran
Funding Free Software
1. Funding GNU Fortran
2. Getting Started
3. What is GNU Fortran?
4. Compile Fortran, C, or Other Programs
5. GNU Fortran Command Options

5.1 Option Summary
5.2 Options Controlling the Kind of Output
5.3 Shorthand Options
5.4 Options Controlling Fortran Dialect
5.5 Options to Request or Suppress Warnings
5.6 Options for Debugging Your Program or GNU Fortran
5.7 Options That Control Optimization
5.8 Options Controlling the Preprocessor
5.9 Options for Directory Search
5.10 Options for Code Generation Conventions
5.11 Environment Variables Affecting GNU Fortran

6. News About GNU Fortran
7. User-visible Changes
8. The GNU Fortran Language

8.1 Direction of Language Development
8.2 ANSI FORTRAN 77 Standard Support

8.2.1 No Passing External Assumed-length
8.2.2 No Passing Dummy Assumed-length
8.2.3 No Pathological Implied-DO
8.2.4 No Useless Implied-DO

8.3 Conformance
8.4 Notation Used in This Chapter
8.5 Fortran Terms and Concepts

8.5.1 Syntactic Items
8.5.2 Statements, Comments, and Lines
8.5.3 Scope of Symbolic Names and Statement Labels

8.6 Characters, Lines, and Execution Sequence

8.6.1 GNU Fortran Character Set
8.6.2 Lines
8.6.3 Continuation Line
8.6.4 Statements
8.6.5 Statement Labels
8.6.6 Order of Statements and Lines
8.6.7 Including Source Text
8.6.8 Cpp-style directives

8.7 Data Types and Constants

8.7.1 Data Types

8.7.1.1 Double Notation
8.7.1.2 Star Notation
8.7.1.3 Kind Notation

8.7.2 Constants
8.7.3 Integer Type
8.7.4 Character Type

8.8 Expressions

8.8.1 The %LOC() Construct

8.9 Specification Statements

8.9.1 NAMELIST Statement
8.9.2 DOUBLE COMPLEX Statement

8.10 Control Statements

8.10.1 DO WHILE
8.10.2 END DO
8.10.3 Construct Names
8.10.4 The CYCLE and EXIT Statements

8.11 Functions and Subroutines

8.11.1 The %VAL() Construct
8.11.2 The %REF() Construct
8.11.3 The %DESCR() Construct
8.11.4 Generics and Specifics
8.11.5 REAL() and AIMAG() of Complex
8.11.6 CMPLX() of DOUBLE PRECISION
8.11.7 MIL-STD 1753 Support
8.11.8 f77/f2c Intrinsics
8.11.9 Table of Intrinsic Functions

8.11.9.1 Abort Intrinsic
8.11.9.2 Abs Intrinsic
8.11.9.3 Access Intrinsic
8.11.9.4 AChar Intrinsic
8.11.9.5 ACos Intrinsic
8.11.9.6 AdjustL Intrinsic
8.11.9.7 AdjustR Intrinsic
8.11.9.8 AImag Intrinsic
8.11.9.9 AInt Intrinsic
8.11.9.10 Alarm Intrinsic
8.11.9.11 All Intrinsic
8.11.9.12 Allocated Intrinsic
8.11.9.13 ALog Intrinsic
8.11.9.14 ALog10 Intrinsic
8.11.9.15 AMax0 Intrinsic
8.11.9.16 AMax1 Intrinsic
8.11.9.17 AMin0 Intrinsic
8.11.9.18 AMin1 Intrinsic
8.11.9.19 AMod Intrinsic
8.11.9.20 And Intrinsic
8.11.9.21 ANInt Intrinsic
8.11.9.22 Any Intrinsic
8.11.9.23 ASin Intrinsic
8.11.9.24 Associated Intrinsic
8.11.9.25 ATan Intrinsic
8.11.9.26 ATan2 Intrinsic
8.11.9.27 BesJ0 Intrinsic
8.11.9.28 BesJ1 Intrinsic
8.11.9.29 BesJN Intrinsic
8.11.9.30 BesY0 Intrinsic
8.11.9.31 BesY1 Intrinsic
8.11.9.32 BesYN Intrinsic
8.11.9.33 Bit_Size Intrinsic
8.11.9.34 BTest Intrinsic
8.11.9.35 CAbs Intrinsic
8.11.9.36 CCos Intrinsic
8.11.9.37 Ceiling Intrinsic
8.11.9.38 CExp Intrinsic
8.11.9.39 Char Intrinsic
8.11.9.40 ChDir Intrinsic (subroutine)
8.11.9.41 ChMod Intrinsic (subroutine)
8.11.9.42 CLog Intrinsic
8.11.9.43 Cmplx Intrinsic
8.11.9.44 Complex Intrinsic
8.11.9.45 Conjg Intrinsic
8.11.9.46 Cos Intrinsic
8.11.9.47 CosH Intrinsic
8.11.9.48 Count Intrinsic
8.11.9.49 CPU_Time Intrinsic
8.11.9.50 CShift Intrinsic
8.11.9.51 CSin Intrinsic
8.11.9.52 CSqRt Intrinsic
8.11.9.53 CTime Intrinsic (subroutine)
8.11.9.54 CTime Intrinsic (function)
8.11.9.55 DAbs Intrinsic
8.11.9.56 DACos Intrinsic
8.11.9.57 DASin Intrinsic
8.11.9.58 DATan Intrinsic
8.11.9.59 DATan2 Intrinsic
8.11.9.60 Date_and_Time Intrinsic
8.11.9.61 DbesJ0 Intrinsic
8.11.9.62 DbesJ1 Intrinsic
8.11.9.63 DbesJN Intrinsic
8.11.9.64 DbesY0 Intrinsic
8.11.9.65 DbesY1 Intrinsic
8.11.9.66 DbesYN Intrinsic
8.11.9.67 Dble Intrinsic
8.11.9.68 DCos Intrinsic
8.11.9.69 DCosH Intrinsic
8.11.9.70 DDiM Intrinsic
8.11.9.71 DErF Intrinsic
8.11.9.72 DErFC Intrinsic
8.11.9.73 DExp Intrinsic
8.11.9.74 Digits Intrinsic
8.11.9.75 DiM Intrinsic
8.11.9.76 DInt Intrinsic
8.11.9.77 DLog Intrinsic
8.11.9.78 DLog10 Intrinsic
8.11.9.79 DMax1 Intrinsic
8.11.9.80 DMin1 Intrinsic
8.11.9.81 DMod Intrinsic
8.11.9.82 DNInt Intrinsic
8.11.9.83 Dot_Product Intrinsic
8.11.9.84 DProd Intrinsic
8.11.9.85 DSign Intrinsic
8.11.9.86 DSin Intrinsic
8.11.9.87 DSinH Intrinsic
8.11.9.88 DSqRt Intrinsic
8.11.9.89 DTan Intrinsic
8.11.9.90 DTanH Intrinsic
8.11.9.91 DTime Intrinsic (subroutine)
8.11.9.92 EOShift Intrinsic
8.11.9.93 Epsilon Intrinsic
8.11.9.94 ErF Intrinsic
8.11.9.95 ErFC Intrinsic
8.11.9.96 ETime Intrinsic (subroutine)
8.11.9.97 ETime Intrinsic (function)
8.11.9.98 Exit Intrinsic
8.11.9.99 Exp Intrinsic
8.11.9.100 Exponent Intrinsic
8.11.9.101 FDate Intrinsic (subroutine)
8.11.9.102 FDate Intrinsic (function)
8.11.9.103 FGet Intrinsic (subroutine)
8.11.9.104 FGetC Intrinsic (subroutine)
8.11.9.105 Float Intrinsic
8.11.9.106 Floor Intrinsic
8.11.9.107 Flush Intrinsic
8.11.9.108 FNum Intrinsic
8.11.9.109 FPut Intrinsic (subroutine)
8.11.9.110 FPutC Intrinsic (subroutine)
8.11.9.111 Fraction Intrinsic
8.11.9.112 FSeek Intrinsic
8.11.9.113 FStat Intrinsic (subroutine)
8.11.9.114 FStat Intrinsic (function)
8.11.9.115 FTell Intrinsic (subroutine)
8.11.9.116 FTell Intrinsic (function)
8.11.9.117 GError Intrinsic
8.11.9.118 GetArg Intrinsic
8.11.9.119 GetCWD Intrinsic (subroutine)
8.11.9.120 GetCWD Intrinsic (function)
8.11.9.121 GetEnv Intrinsic
8.11.9.122 GetGId Intrinsic
8.11.9.123 GetLog Intrinsic
8.11.9.124 GetPId Intrinsic
8.11.9.125 GetUId Intrinsic
8.11.9.126 GMTime Intrinsic
8.11.9.127 HostNm Intrinsic (subroutine)
8.11.9.128 HostNm Intrinsic (function)
8.11.9.129 Huge Intrinsic
8.11.9.130 IAbs Intrinsic
8.11.9.131 IAChar Intrinsic
8.11.9.132 IAnd Intrinsic
8.11.9.133 IArgC Intrinsic
8.11.9.134 IBClr Intrinsic
8.11.9.135 IBits Intrinsic
8.11.9.136 IBSet Intrinsic
8.11.9.137 IChar Intrinsic
8.11.9.138 IDate Intrinsic (UNIX)
8.11.9.139 IDiM Intrinsic
8.11.9.140 IDInt Intrinsic
8.11.9.141 IDNInt Intrinsic
8.11.9.142 IEOr Intrinsic
8.11.9.143 IErrNo Intrinsic
8.11.9.144 IFix Intrinsic
8.11.9.145 Imag Intrinsic
8.11.9.146 ImagPart Intrinsic
8.11.9.147 Index Intrinsic
8.11.9.148 Int Intrinsic
8.11.9.149 Int2 Intrinsic
8.11.9.150 Int8 Intrinsic
8.11.9.151 IOr Intrinsic
8.11.9.152 IRand Intrinsic
8.11.9.153 IsaTty Intrinsic
8.11.9.154 IShft Intrinsic
8.11.9.155 IShftC Intrinsic
8.11.9.156 ISign Intrinsic
8.11.9.157 ITime Intrinsic
8.11.9.158 Kill Intrinsic (subroutine)
8.11.9.159 Kind Intrinsic
8.11.9.160 LBound Intrinsic
8.11.9.161 Len Intrinsic
8.11.9.162 Len_Trim Intrinsic
8.11.9.163 LGe Intrinsic
8.11.9.164 LGt Intrinsic
8.11.9.165 Link Intrinsic (subroutine)
8.11.9.166 LLe Intrinsic
8.11.9.167 LLt Intrinsic
8.11.9.168 LnBlnk Intrinsic
8.11.9.169 Loc Intrinsic
8.11.9.170 Log Intrinsic
8.11.9.171 Log10 Intrinsic
8.11.9.172 Logical Intrinsic
8.11.9.173 Long Intrinsic
8.11.9.174 LShift Intrinsic
8.11.9.175 LStat Intrinsic (subroutine)
8.11.9.176 LStat Intrinsic (function)
8.11.9.177 LTime Intrinsic
8.11.9.178 MatMul Intrinsic
8.11.9.179 Max Intrinsic
8.11.9.180 Max0 Intrinsic
8.11.9.181 Max1 Intrinsic
8.11.9.182 MaxExponent Intrinsic
8.11.9.183 MaxLoc Intrinsic
8.11.9.184 MaxVal Intrinsic
8.11.9.185 MClock Intrinsic
8.11.9.186 MClock8 Intrinsic
8.11.9.187 Merge Intrinsic
8.11.9.188 Min Intrinsic
8.11.9.189 Min0 Intrinsic
8.11.9.190 Min1 Intrinsic
8.11.9.191 MinExponent Intrinsic
8.11.9.192 MinLoc Intrinsic
8.11.9.193 MinVal Intrinsic
8.11.9.194 Mod Intrinsic
8.11.9.195 Modulo Intrinsic
8.11.9.196 MvBits Intrinsic
8.11.9.197 Nearest Intrinsic
8.11.9.198 NInt Intrinsic
8.11.9.199 Not Intrinsic
8.11.9.200 Or Intrinsic
8.11.9.201 Pack Intrinsic
8.11.9.202 PError Intrinsic
8.11.9.203 Precision Intrinsic
8.11.9.204 Present Intrinsic
8.11.9.205 Product Intrinsic
8.11.9.206 Radix Intrinsic
8.11.9.207 Rand Intrinsic
8.11.9.208 Random_Number Intrinsic
8.11.9.209 Random_Seed Intrinsic
8.11.9.210 Range Intrinsic
8.11.9.211 Real Intrinsic
8.11.9.212 RealPart Intrinsic
8.11.9.213 Rename Intrinsic (subroutine)
8.11.9.214 Repeat Intrinsic
8.11.9.215 Reshape Intrinsic
8.11.9.216 RRSpacing Intrinsic
8.11.9.217 RShift Intrinsic
8.11.9.218 Scale Intrinsic
8.11.9.219 Scan Intrinsic
8.11.9.220 Second Intrinsic (function)
8.11.9.221 Second Intrinsic (subroutine)
8.11.9.222 Selected_Int_Kind Intrinsic
8.11.9.223 Selected_Real_Kind Intrinsic
8.11.9.224 Set_Exponent Intrinsic
8.11.9.225 Shape Intrinsic
8.11.9.226 Short Intrinsic
8.11.9.227 Sign Intrinsic
8.11.9.228 Signal Intrinsic (subroutine)
8.11.9.229 Sin Intrinsic
8.11.9.230 SinH Intrinsic
8.11.9.231 Sleep Intrinsic
8.11.9.232 Sngl Intrinsic
8.11.9.233 Spacing Intrinsic
8.11.9.234 Spread Intrinsic
8.11.9.235 SqRt Intrinsic
8.11.9.236 SRand Intrinsic
8.11.9.237 Stat Intrinsic (subroutine)
8.11.9.238 Stat Intrinsic (function)
8.11.9.239 Sum Intrinsic
8.11.9.240 SymLnk Intrinsic (subroutine)
8.11.9.241 System Intrinsic (subroutine)
8.11.9.242 System_Clock Intrinsic
8.11.9.243 Tan Intrinsic
8.11.9.244 TanH Intrinsic
8.11.9.245 Time Intrinsic (UNIX)
8.11.9.246 Time8 Intrinsic
8.11.9.247 Tiny Intrinsic
8.11.9.248 Transfer Intrinsic
8.11.9.249 Transpose Intrinsic
8.11.9.250 Trim Intrinsic
8.11.9.251 TtyNam Intrinsic (subroutine)
8.11.9.252 TtyNam Intrinsic (function)
8.11.9.253 UBound Intrinsic
8.11.9.254 UMask Intrinsic (subroutine)
8.11.9.255 Unlink Intrinsic (subroutine)
8.11.9.256 Unpack Intrinsic
8.11.9.257 Verify Intrinsic
8.11.9.258 XOr Intrinsic
8.11.9.259 ZAbs Intrinsic
8.11.9.260 ZCos Intrinsic
8.11.9.261 ZExp Intrinsic
8.11.9.262 ZLog Intrinsic
8.11.9.263 ZSin Intrinsic
8.11.9.264 ZSqRt Intrinsic

8.12 Scope and Classes of Symbolic Names

8.12.1 Underscores in Symbol Names

8.13 I/O
8.14 Fortran 90 Features

9. Other Dialects

9.1 Source Form

9.1.1 Carriage Returns
9.1.2 Tabs
9.1.3 Short Lines
9.1.4 Long Lines
9.1.5 Ampersand Continuation Line

9.2 Trailing Comment
9.3 Debug Line
9.4 Dollar Signs in Symbol Names
9.5 Case Sensitivity
9.6 VXT Fortran

9.6.1 Meaning of Double Quote
9.6.2 Meaning of Exclamation Point in Column 6

9.7 Fortran 90
9.8 Pedantic Compilation
9.9 Distensions

9.9.1 Implicit Argument Conversion
9.9.2 Ugly Assumed-Size Arrays
9.9.3 Ugly Complex Part Extraction
9.9.4 Ugly Null Arguments
9.9.5 Ugly Conversion of Initializers
9.9.6 Ugly Integer Conversions
9.9.7 Ugly Assigned Labels

10. The GNU Fortran Compiler

10.1 Compiler Limits
10.2 Run-time Environment Limits

10.2.1 Timer Wraparounds
10.2.2 Year 2000 (Y2K) Problems
10.2.3 Array Size
10.2.4 Character-variable Length
10.2.5 Year 10000 (Y10K) Problems

10.3 Compiler Types
10.4 Compiler Constants
10.5 Compiler Intrinsics

10.5.1 Intrinsic Groups
10.5.2 Other Intrinsics

10.5.2.1 ACosD Intrinsic
10.5.2.2 AIMax0 Intrinsic
10.5.2.3 AIMin0 Intrinsic
10.5.2.4 AJMax0 Intrinsic
10.5.2.5 AJMin0 Intrinsic
10.5.2.6 ASinD Intrinsic
10.5.2.7 ATan2D Intrinsic
10.5.2.8 ATanD Intrinsic
10.5.2.9 BITest Intrinsic
10.5.2.10 BJTest Intrinsic
10.5.2.11 CDAbs Intrinsic
10.5.2.12 CDCos Intrinsic
10.5.2.13 CDExp Intrinsic
10.5.2.14 CDLog Intrinsic
10.5.2.15 CDSin Intrinsic
10.5.2.16 CDSqRt Intrinsic
10.5.2.17 ChDir Intrinsic (function)
10.5.2.18 ChMod Intrinsic (function)
10.5.2.19 CosD Intrinsic
10.5.2.20 DACosD Intrinsic
10.5.2.21 DASinD Intrinsic
10.5.2.22 DATan2D Intrinsic
10.5.2.23 DATanD Intrinsic
10.5.2.24 Date Intrinsic
10.5.2.25 DbleQ Intrinsic
10.5.2.26 DCmplx Intrinsic
10.5.2.27 DConjg Intrinsic
10.5.2.28 DCosD Intrinsic
10.5.2.29 DFloat Intrinsic
10.5.2.30 DFlotI Intrinsic
10.5.2.31 DFlotJ Intrinsic
10.5.2.32 DImag Intrinsic
10.5.2.33 DReal Intrinsic
10.5.2.34 DSinD Intrinsic
10.5.2.35 DTanD Intrinsic
10.5.2.36 DTime Intrinsic (function)
10.5.2.37 FGet Intrinsic (function)
10.5.2.38 FGetC Intrinsic (function)
10.5.2.39 FloatI Intrinsic
10.5.2.40 FloatJ Intrinsic
10.5.2.41 FPut Intrinsic (function)
10.5.2.42 FPutC Intrinsic (function)
10.5.2.43 IDate Intrinsic (VXT)
10.5.2.44 IIAbs Intrinsic
10.5.2.45 IIAnd Intrinsic
10.5.2.46 IIBClr Intrinsic
10.5.2.47 IIBits Intrinsic
10.5.2.48 IIBSet Intrinsic
10.5.2.49 IIDiM Intrinsic
10.5.2.50 IIDInt Intrinsic
10.5.2.51 IIDNnt Intrinsic
10.5.2.52 IIEOr Intrinsic
10.5.2.53 IIFix Intrinsic
10.5.2.54 IInt Intrinsic
10.5.2.55 IIOr Intrinsic
10.5.2.56 IIQint Intrinsic
10.5.2.57 IIQNnt Intrinsic
10.5.2.58 IIShftC Intrinsic
10.5.2.59 IISign Intrinsic
10.5.2.60 IMax0 Intrinsic
10.5.2.61 IMax1 Intrinsic
10.5.2.62 IMin0 Intrinsic
10.5.2.63 IMin1 Intrinsic
10.5.2.64 IMod Intrinsic
10.5.2.65 INInt Intrinsic
10.5.2.66 INot Intrinsic
10.5.2.67 IZExt Intrinsic
10.5.2.68 JIAbs Intrinsic
10.5.2.69 JIAnd Intrinsic
10.5.2.70 JIBClr Intrinsic
10.5.2.71 JIBits Intrinsic
10.5.2.72 JIBSet Intrinsic
10.5.2.73 JIDiM Intrinsic
10.5.2.74 JIDInt Intrinsic
10.5.2.75 JIDNnt Intrinsic
10.5.2.76 JIEOr Intrinsic
10.5.2.77 JIFix Intrinsic
10.5.2.78 JInt Intrinsic
10.5.2.79 JIOr Intrinsic
10.5.2.80 JIQint Intrinsic
10.5.2.81 JIQNnt Intrinsic
10.5.2.82 JIShft Intrinsic
10.5.2.83 JIShftC Intrinsic
10.5.2.84 JISign Intrinsic
10.5.2.85 JMax0 Intrinsic
10.5.2.86 JMax1 Intrinsic
10.5.2.87 JMin0 Intrinsic
10.5.2.88 JMin1 Intrinsic
10.5.2.89 JMod Intrinsic
10.5.2.90 JNInt Intrinsic
10.5.2.91 JNot Intrinsic
10.5.2.92 JZExt Intrinsic
10.5.2.93 Kill Intrinsic (function)
10.5.2.94 Link Intrinsic (function)
10.5.2.95 QAbs Intrinsic
10.5.2.96 QACos Intrinsic
10.5.2.97 QACosD Intrinsic
10.5.2.98 QASin Intrinsic
10.5.2.99 QASinD Intrinsic
10.5.2.100 QATan Intrinsic
10.5.2.101 QATan2 Intrinsic
10.5.2.102 QATan2D Intrinsic
10.5.2.103 QATanD Intrinsic
10.5.2.104 QCos Intrinsic
10.5.2.105 QCosD Intrinsic
10.5.2.106 QCosH Intrinsic
10.5.2.107 QDiM Intrinsic
10.5.2.108 QExp Intrinsic
10.5.2.109 QExt Intrinsic
10.5.2.110 QExtD Intrinsic
10.5.2.111 QFloat Intrinsic
10.5.2.112 QInt Intrinsic
10.5.2.113 QLog Intrinsic
10.5.2.114 QLog10 Intrinsic
10.5.2.115 QMax1 Intrinsic
10.5.2.116 QMin1 Intrinsic
10.5.2.117 QMod Intrinsic
10.5.2.118 QNInt Intrinsic
10.5.2.119 QSin Intrinsic
10.5.2.120 QSinD Intrinsic
10.5.2.121 QSinH Intrinsic
10.5.2.122 QSqRt Intrinsic
10.5.2.123 QTan Intrinsic
10.5.2.124 QTanD Intrinsic
10.5.2.125 QTanH Intrinsic
10.5.2.126 Rename Intrinsic (function)
10.5.2.127 Secnds Intrinsic
10.5.2.128 Signal Intrinsic (function)
10.5.2.129 SinD Intrinsic
10.5.2.130 SnglQ Intrinsic
10.5.2.131 SymLnk Intrinsic (function)
10.5.2.132 System Intrinsic (function)
10.5.2.133 TanD Intrinsic
10.5.2.134 Time Intrinsic (VXT)
10.5.2.135 UMask Intrinsic (function)
10.5.2.136 Unlink Intrinsic (function)
10.5.2.137 ZExt Intrinsic

11. Other Compilers

11.1 Dropping f2c Compatibility
11.2 Compilers Other Than f2c

12. Other Languages

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

12.1.1 C Interfacing Tools
12.1.2 Accessing Type Information in C
12.1.3 Generating Skeletons and Prototypes with f2c
12.1.4 C++ Considerations
12.1.5 Startup Code

13. Debugging and Interfacing

13.1 Main Program Unit (PROGRAM)
13.2 Procedures (SUBROUTINE and FUNCTION)
13.3 Functions (FUNCTION and RETURN)
13.4 Names
13.5 Common Blocks (COMMON)
13.6 Local Equivalence Areas (EQUIVALENCE)
13.7 Complex Variables (COMPLEX)
13.8 Arrays (DIMENSION)
13.9 Adjustable Arrays (DIMENSION)
13.10 Alternate Entry Points (ENTRY)
13.11 Alternate Returns (SUBROUTINE and RETURN)
13.12 Assigned Statement Labels (ASSIGN and GOTO)
13.13 Run-time Library Errors

14. Collected Fortran Wisdom

14.1 Advantages Over f2c

14.1.1 Language Extensions
14.1.2 Diagnostic Abilities
14.1.3 Compiler Options
14.1.4 Compiler Speed
14.1.5 Program Speed
14.1.6 Ease of Debugging
14.1.7 Character and Hollerith Constants

14.2 Block Data and Libraries
14.3 Loops
14.4 Working Programs

14.4.1 Not My Type
14.4.2 Variables Assumed To Be Zero
14.4.3 Variables Assumed To Be Saved
14.4.4 Unwanted Variables
14.4.5 Unused Arguments
14.4.6 Surprising Interpretations of Code
14.4.7 Aliasing Assumed To Work
14.4.8 Output Assumed To Flush
14.4.9 Large File Unit Numbers
14.4.10 Floating-point precision
14.4.11 Inconsistent Calling Sequences

14.5 Overly Convenient Command-line Options
14.6 Faster Programs

14.6.1 Aligned Data
14.6.2 Prefer Automatic Uninitialized Variables
14.6.3 Avoid f2c Compatibility
14.6.4 Use Submodel Options

15. Known Causes of Trouble with GNU Fortran

15.1 Bugs Not In GNU Fortran

15.1.1 Signal 11 and Friends
15.1.2 Cannot Link Fortran Programs
15.1.3 Large Common Blocks
15.1.4 Debugger Problems
15.1.5 NeXTStep Problems
15.1.6 Stack Overflow
15.1.7 Nothing Happens
15.1.8 Strange Behavior at Run Time
15.1.9 Floating-point Errors

15.2 Known Bugs In GNU Fortran
15.3 Missing Features

15.3.1 Better Source Model
15.3.2 Fortran 90 Support
15.3.3 Intrinsics in PARAMETER Statements
15.3.4 Arbitrary Concatenation
15.3.5 SELECT CASE on CHARACTER Type
15.3.6 RECURSIVE Keyword
15.3.7 Increasing Precision/Range
15.3.8 Popular Non-standard Types
15.3.9 Full Support for Compiler Types
15.3.10 Array Bounds Expressions
15.3.11 POINTER Statements
15.3.12 Sensible Non-standard Constructs
15.3.13 READONLY Keyword
15.3.14 FLUSH Statement
15.3.15 Expressions in FORMAT Statements
15.3.16 Explicit Assembler Code
15.3.17 Q Edit Descriptor
15.3.18 Old-style PARAMETER Statements
15.3.19 TYPE and ACCEPT I/O Statements
15.3.20 STRUCTURE, UNION, RECORD, MAP
15.3.21 OPEN, CLOSE, and INQUIRE Keywords
15.3.22 ENCODE and DECODE
15.3.23 AUTOMATIC Statement
15.3.24 Suppressing Space Padding of Source Lines
15.3.25 Fortran Preprocessor
15.3.26 Bit Operations on Floating-point Data
15.3.27 Really Ugly Character Assignments
15.3.28 POSIX Standard
15.3.29 Floating-point Exception Handling
15.3.30 Nonportable Conversions
15.3.31 Large Automatic Arrays
15.3.32 Support for Threads
15.3.33 Enabling Debug Lines
15.3.34 Better Warnings
15.3.35 Gracefully Handle Sensible Bad Code
15.3.36 Non-standard Conversions
15.3.37 Non-standard Intrinsics
15.3.38 Modifying DO Variable
15.3.39 Better Pedantic Compilation
15.3.40 Warn About Implicit Conversions
15.3.41 Invalid Use of Hollerith Constant
15.3.42 Dummy Array Without Dimensioning Dummy
15.3.43 Invalid FORMAT Specifiers
15.3.44 Ambiguous Dialects
15.3.45 Unused Labels
15.3.46 Informational Messages
15.3.47 Uninitialized Variables at Run Time
15.3.48 Portable Unformatted Files
15.3.49 Better List-directed I/O
15.3.50 Default to Console I/O
15.3.51 Labels Visible to Debugger

15.4 Disappointments and Misunderstandings

15.4.1 Mangling of Names in Source Code
15.4.2 Multiple Definitions of External Names
15.4.3 Limitation on Implicit Declarations

15.5 Certain Changes We Don't Want to Make

15.5.1 Backslash in Constants
15.5.2 Initializing Before Specifying
15.5.3 Context-Sensitive Intrinsicness
15.5.4 Context-Sensitive Constants
15.5.5 Equivalence Versus Equality
15.5.6 Order of Side Effects

15.6 Warning Messages and Error Messages

16. Open Questions
17. Reporting Bugs

17.1 Have You Found a Bug?
17.2 Where to Report Bugs
17.3 How to Report Bugs

18. How To Get Help with GNU Fortran
19. Adding Options
20. Projects

20.1 Improve Efficiency
20.2 Better Optimization
20.3 Simplify Porting
20.4 More Extensions
20.5 Machine Model
20.6 Internals Documentation
20.7 Internals Improvements
20.8 Better Diagnostics

21. Front End

21.1 Overview of Sources
21.2 Overview of Translation Process

21.2.1 g77stripcard
21.2.2 lex.c
21.2.3 sta.c
21.2.4 sti.c
21.2.5 stq.c
21.2.6 stb.c
21.2.7 expr.c
21.2.8 stc.c
21.2.9 std.c
21.2.10 ste.c
21.2.11 Gotchas (Transforming)

21.2.11.1 Multi-character Lexemes
21.2.11.2 Space-padding Lexemes
21.2.11.3 Bizarre Free-form Hollerith Constants
21.2.11.4 Hollerith Constants
21.2.11.5 Confusing Function Keyword
21.2.11.6 Weird READ

21.2.12 TBD (Transforming)

21.3 Philosophy of Code Generation
21.4 Two-pass Design

21.4.1 Two-pass Code
21.4.2 Why Two Passes

21.5 Challenges Posed
21.6 Transforming Statements

21.6.1 Statements Needing Temporaries
21.6.2 Transforming DO WHILE
21.6.3 Transforming Iterative DO
21.6.4 Transforming Block IF
21.6.5 Transforming SELECT CASE

21.7 Transforming Expressions
21.8 Internal Naming Conventions

22. Diagnostics

22.1 CMPAMBIG
22.2 EXPIMP
22.3 INTGLOB
22.4 LEX
22.5 GLOBALS
22.6 LINKFAIL
22.7 Y2KBAD

Index