diff options
Diffstat (limited to 'share/doc/gfortran/Error-and-Warning-Options.html')
| -rw-r--r-- | share/doc/gfortran/Error-and-Warning-Options.html | 511 |
1 files changed, 511 insertions, 0 deletions
diff --git a/share/doc/gfortran/Error-and-Warning-Options.html b/share/doc/gfortran/Error-and-Warning-Options.html new file mode 100644 index 0000000..69d38d1 --- /dev/null +++ b/share/doc/gfortran/Error-and-Warning-Options.html @@ -0,0 +1,511 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> +<html> +<!-- Copyright (C) 1999-2023 Free Software Foundation, Inc. + +Permission is granted to copy, distribute and/or modify this document +under the terms of the GNU Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being "Funding Free Software", the Front-Cover +Texts being (a) (see below), and with the Back-Cover Texts being (b) +(see below). A copy of the license is included in the section entitled +"GNU Free Documentation License". + +(a) The FSF's Front-Cover Text is: + +A GNU Manual + +(b) The FSF's Back-Cover Text is: + +You have freedom to copy and modify this GNU Manual, like GNU + software. Copies published by the Free Software Foundation raise + funds for GNU development. --> +<!-- Created by GNU Texinfo 5.1, http://www.gnu.org/software/texinfo/ --> +<head> +<title>The GNU Fortran Compiler: Error and Warning Options</title> + +<meta name="description" content="The GNU Fortran Compiler: Error and Warning Options"> +<meta name="keywords" content="The GNU Fortran Compiler: Error and Warning Options"> +<meta name="resource-type" content="document"> +<meta name="distribution" content="global"> +<meta name="Generator" content="makeinfo"> +<meta http-equiv="Content-Type" content="text/html; charset=utf-8"> +<link href="index.html#Top" rel="start" title="Top"> +<link href="Option-Index.html#Option-Index" rel="index" title="Option Index"> +<link href="index.html#SEC_Contents" rel="contents" title="Table of Contents"> +<link href="Invoking-GNU-Fortran.html#Invoking-GNU-Fortran" rel="up" title="Invoking GNU Fortran"> +<link href="Debugging-Options.html#Debugging-Options" rel="next" title="Debugging Options"> +<link href="Preprocessing-Options.html#Preprocessing-Options" rel="previous" title="Preprocessing Options"> +<style type="text/css"> +<!-- +a.summary-letter {text-decoration: none} +blockquote.smallquotation {font-size: smaller} +div.display {margin-left: 3.2em} +div.example {margin-left: 3.2em} +div.indentedblock {margin-left: 3.2em} +div.lisp {margin-left: 3.2em} +div.smalldisplay {margin-left: 3.2em} +div.smallexample {margin-left: 3.2em} +div.smallindentedblock {margin-left: 3.2em; font-size: smaller} +div.smalllisp {margin-left: 3.2em} +kbd {font-style:oblique} +pre.display {font-family: inherit} +pre.format {font-family: inherit} +pre.menu-comment {font-family: serif} +pre.menu-preformatted {font-family: serif} +pre.smalldisplay {font-family: inherit; font-size: smaller} +pre.smallexample {font-size: smaller} +pre.smallformat {font-family: inherit; font-size: smaller} +pre.smalllisp {font-size: smaller} +span.nocodebreak {white-space:nowrap} +span.nolinebreak {white-space:nowrap} +span.roman {font-family:serif; font-weight:normal} +span.sansserif {font-family:sans-serif; font-weight:normal} +ul.no-bullet {list-style: none} +--> +</style> + + +</head> + +<body lang="en" bgcolor="#FFFFFF" text="#000000" link="#0000FF" vlink="#800080" alink="#FF0000"> +<a name="Error-and-Warning-Options"></a> +<div class="header"> +<p> +Next: <a href="Debugging-Options.html#Debugging-Options" accesskey="n" rel="next">Debugging Options</a>, Previous: <a href="Preprocessing-Options.html#Preprocessing-Options" accesskey="p" rel="previous">Preprocessing Options</a>, Up: <a href="Invoking-GNU-Fortran.html#Invoking-GNU-Fortran" accesskey="u" rel="up">Invoking GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> +<hr> +<a name="Options-to-request-or-suppress-errors-and-warnings"></a> +<h3 class="section">2.4 Options to request or suppress errors and warnings</h3> +<a name="index-options_002c-warnings"></a> +<a name="index-options_002c-errors"></a> +<a name="index-warnings_002c-suppressing"></a> +<a name="index-messages_002c-error"></a> +<a name="index-messages_002c-warning"></a> +<a name="index-suppressing-warnings"></a> + +<p>Errors are diagnostic messages that report that the GNU Fortran compiler +cannot compile the relevant piece of source code. The compiler will +continue to process the program in an attempt to report further errors +to aid in debugging, but will not produce any compiled output. +</p> +<p>Warnings are diagnostic messages that report constructions which +are not inherently erroneous but which are risky or suggest there is +likely to be a bug in the program. Unless <samp>-Werror</samp> is specified, +they do not prevent compilation of the program. +</p> +<p>You can request many specific warnings with options beginning <samp>-W</samp>, +for example <samp>-Wimplicit</samp> to request warnings on implicit +declarations. Each of these specific warning options also has a +negative form beginning <samp>-Wno-</samp> to turn off warnings; +for example, <samp>-Wno-implicit</samp>. This manual lists only one of the +two forms, whichever is not the default. +</p> +<p>These options control the amount and kinds of errors and warnings produced +by GNU Fortran: +</p> +<dl compact="compact"> +<dd><a name="index-fmax_002derrors_003dn"></a> +<a name="index-errors_002c-limiting"></a> +</dd> +<dt><code>-fmax-errors=<var>n</var></code></dt> +<dd><p>Limits the maximum number of error messages to <var>n</var>, at which point +GNU Fortran bails out rather than attempting to continue processing the +source code. If <var>n</var> is 0, there is no limit on the number of error +messages produced. +</p> +<a name="index-fsyntax_002donly"></a> +<a name="index-syntax-checking"></a> +</dd> +<dt><code>-fsyntax-only</code></dt> +<dd><p>Check the code for syntax errors, but do not actually compile it. This +will generate module files for each module present in the code, but no +other output file. +</p> +<a name="index-pedantic"></a> +<a name="index-Wpedantic"></a> +</dd> +<dt><code>-Wpedantic</code></dt> +<dt><code>-pedantic</code></dt> +<dd><p>Issue warnings for uses of extensions to Fortran. +<samp>-pedantic</samp> also applies to C-language constructs where they +occur in GNU Fortran source files, such as use of ‘<samp>\e</samp>’ in a +character constant within a directive like <code>#include</code>. +</p> +<p>Valid Fortran programs should compile properly with or without +this option. +However, without this option, certain GNU extensions and traditional +Fortran features are supported as well. +With this option, many of them are rejected. +</p> +<p>Some users try to use <samp>-pedantic</samp> to check programs for conformance. +They soon find that it does not do quite what they want—it finds some +nonstandard practices, but not all. +However, improvements to GNU Fortran in this area are welcome. +</p> +<p>This should be used in conjunction with <samp>-std=f95</samp>, +<samp>-std=f2003</samp>, <samp>-std=f2008</samp> or <samp>-std=f2018</samp>. +</p> +<a name="index-pedantic_002derrors"></a> +</dd> +<dt><code>-pedantic-errors</code></dt> +<dd><p>Like <samp>-pedantic</samp>, except that errors are produced rather than +warnings. +</p> +<a name="index-Wall"></a> +<a name="index-all-warnings"></a> +<a name="index-warnings_002c-all"></a> +</dd> +<dt><code>-Wall</code></dt> +<dd><p>Enables commonly used warning options pertaining to usage that +we recommend avoiding and that we believe are easy to avoid. +This currently includes <samp>-Waliasing</samp>, <samp>-Wampersand</samp>, +<samp>-Wconversion</samp>, <samp>-Wsurprising</samp>, <samp>-Wc-binding-type</samp>, +<samp>-Wintrinsics-std</samp>, <samp>-Wtabs</samp>, <samp>-Wintrinsic-shadow</samp>, +<samp>-Wline-truncation</samp>, <samp>-Wtarget-lifetime</samp>, +<samp>-Winteger-division</samp>, <samp>-Wreal-q-constant</samp>, <samp>-Wunused</samp> +and <samp>-Wundefined-do-loop</samp>. +</p> +<a name="index-Waliasing"></a> +<a name="index-aliasing"></a> +<a name="index-warnings_002c-aliasing"></a> +</dd> +<dt><code>-Waliasing</code></dt> +<dd><p>Warn about possible aliasing of dummy arguments. Specifically, it warns +if the same actual argument is associated with a dummy argument with +<code>INTENT(IN)</code> and a dummy argument with <code>INTENT(OUT)</code> in a call +with an explicit interface. +</p> +<p>The following example will trigger the warning. +</p><div class="smallexample"> +<pre class="smallexample"> interface + subroutine bar(a,b) + integer, intent(in) :: a + integer, intent(out) :: b + end subroutine + end interface + integer :: a + + call bar(a,a) +</pre></div> + +<a name="index-Wampersand"></a> +<a name="index-warnings_002c-ampersand"></a> +<a name="index-_0026"></a> +</dd> +<dt><code>-Wampersand</code></dt> +<dd><p>Warn about missing ampersand in continued character constants. The +warning is given with <samp>-Wampersand</samp>, <samp>-pedantic</samp>, +<samp>-std=f95</samp>, <samp>-std=f2003</samp>, <samp>-std=f2008</samp> and +<samp>-std=f2018</samp>. Note: With no ampersand given in a continued +character constant, GNU Fortran assumes continuation at the first +non-comment, non-whitespace character after the ampersand that +initiated the continuation. +</p> +<a name="index-Warray_002dtemporaries"></a> +<a name="index-warnings_002c-array-temporaries"></a> +</dd> +<dt><code>-Warray-temporaries</code></dt> +<dd><p>Warn about array temporaries generated by the compiler. The information +generated by this warning is sometimes useful in optimization, in order to +avoid such temporaries. +</p> +<a name="index-Wc_002dbinding_002dtype"></a> +<a name="index-warning_002c-C-binding-type"></a> +</dd> +<dt><code>-Wc-binding-type</code></dt> +<dd><p>Warn if the a variable might not be C interoperable. In particular, warn if +the variable has been declared using an intrinsic type with default kind +instead of using a kind parameter defined for C interoperability in the +intrinsic <code>ISO_C_Binding</code> module. This option is implied by +<samp>-Wall</samp>. +</p> +<a name="index-Wcharacter_002dtruncation"></a> +<a name="index-warnings_002c-character-truncation"></a> +</dd> +<dt><code>-Wcharacter-truncation</code></dt> +<dd><p>Warn when a character assignment will truncate the assigned string. +</p> +<a name="index-Wline_002dtruncation"></a> +<a name="index-warnings_002c-line-truncation"></a> +</dd> +<dt><code>-Wline-truncation</code></dt> +<dd><p>Warn when a source code line will be truncated. This option is +implied by <samp>-Wall</samp>. For free-form source code, the default is +<samp>-Werror=line-truncation</samp> such that truncations are reported as +error. +</p> +<a name="index-Wconversion"></a> +<a name="index-warnings_002c-conversion"></a> +<a name="index-conversion"></a> +</dd> +<dt><code>-Wconversion</code></dt> +<dd><p>Warn about implicit conversions that are likely to change the value of +the expression after conversion. Implied by <samp>-Wall</samp>. +</p> +<a name="index-Wconversion_002dextra"></a> +<a name="index-warnings_002c-conversion-1"></a> +<a name="index-conversion-1"></a> +</dd> +<dt><code>-Wconversion-extra</code></dt> +<dd><p>Warn about implicit conversions between different types and kinds. This +option does <em>not</em> imply <samp>-Wconversion</samp>. +</p> +<a name="index-Wextra"></a> +<a name="index-extra-warnings"></a> +<a name="index-warnings_002c-extra"></a> +</dd> +<dt><code>-Wextra</code></dt> +<dd><p>Enables some warning options for usages of language features which +may be problematic. This currently includes <samp>-Wcompare-reals</samp>, +<samp>-Wunused-parameter</samp> and <samp>-Wdo-subscript</samp>. +</p> +<a name="index-Wfrontend_002dloop_002dinterchange"></a> +<a name="index-warnings_002c-loop-interchange"></a> +<a name="index-loop-interchange_002c-warning"></a> +</dd> +<dt><code>-Wfrontend-loop-interchange</code></dt> +<dd><p>Warn when using <samp>-ffrontend-loop-interchange</samp> for performing loop +interchanges. +</p> +<a name="index-Wimplicit_002dinterface"></a> +<a name="index-warnings_002c-implicit-interface"></a> +</dd> +<dt><code>-Wimplicit-interface</code></dt> +<dd><p>Warn if a procedure is called without an explicit interface. +Note this only checks that an explicit interface is present. It does not +check that the declared interfaces are consistent across program units. +</p> +<a name="index-Wimplicit_002dprocedure"></a> +<a name="index-warnings_002c-implicit-procedure"></a> +</dd> +<dt><code>-Wimplicit-procedure</code></dt> +<dd><p>Warn if a procedure is called that has neither an explicit interface +nor has been declared as <code>EXTERNAL</code>. +</p> +<a name="index-Winteger_002ddivision"></a> +<a name="index-warnings_002c-integer-division"></a> +<a name="index-warnings_002c-division-of-integers"></a> +</dd> +<dt><code>-Winteger-division</code></dt> +<dd><p>Warn if a constant integer division truncates its result. +As an example, 3/5 evaluates to 0. +</p> +<a name="index-Wintrinsics_002dstd"></a> +<a name="index-warnings_002c-non_002dstandard-intrinsics"></a> +<a name="index-warnings_002c-intrinsics-of-other-standards"></a> +</dd> +<dt><code>-Wintrinsics-std</code></dt> +<dd><p>Warn if <code>gfortran</code> finds a procedure named like an intrinsic not +available in the currently selected standard (with <samp>-std</samp>) and treats +it as <code>EXTERNAL</code> procedure because of this. <samp>-fall-intrinsics</samp> can +be used to never trigger this behavior and always link to the intrinsic +regardless of the selected standard. +</p> +<a name="index-Woverwrite_002drecursive"></a> +<a name="index-warnings_002c-overwrite-recursive"></a> +</dd> +<dt><code>-Wno-overwrite-recursive</code></dt> +<dd><p>Do not warn when <samp>-fno-automatic</samp> is used with <samp>-frecursive</samp>. Recursion +will be broken if the relevant local variables do not have the attribute +<code>AUTOMATIC</code> explicitly declared. This option can be used to suppress the warning +when it is known that recursion is not broken. Useful for build environments that use +<samp>-Werror</samp>. +</p> +<a name="index-Wreal_002dq_002dconstant"></a> +<a name="index-warnings_002c-q-exponent_002dletter"></a> +</dd> +<dt><code>-Wreal-q-constant</code></dt> +<dd><p>Produce a warning if a real-literal-constant contains a <code>q</code> +exponent-letter. +</p> +<a name="index-Wsurprising"></a> +<a name="index-warnings_002c-suspicious-code"></a> +</dd> +<dt><code>-Wsurprising</code></dt> +<dd><p>Produce a warning when “suspicious” code constructs are encountered. +While technically legal these usually indicate that an error has been made. +</p> +<p>This currently produces a warning under the following circumstances: +</p> +<ul> +<li> An INTEGER SELECT construct has a CASE that can never be matched as its +lower value is greater than its upper value. + +</li><li> A LOGICAL SELECT construct has three CASE statements. + +</li><li> A TRANSFER specifies a source that is shorter than the destination. + +</li><li> The type of a function result is declared more than once with the same type. If +<samp>-pedantic</samp> or standard-conforming mode is enabled, this is an error. + +</li><li> A <code>CHARACTER</code> variable is declared with negative length. + +</li><li> With <samp>-fopenmp</samp>, for fixed-form source code, when an <code>omx</code> +vendor-extension sentinel is encountered. (The equivalent <code>ompx</code>, +used in free-form source code, is diagnosed by default.) +</li></ul> + +<a name="index-Wtabs"></a> +<a name="index-warnings_002c-tabs"></a> +<a name="index-tabulators"></a> +</dd> +<dt><code>-Wtabs</code></dt> +<dd><p>By default, tabs are accepted as whitespace, but tabs are not members +of the Fortran Character Set. For continuation lines, a tab followed +by a digit between 1 and 9 is supported. <samp>-Wtabs</samp> will cause a +warning to be issued if a tab is encountered. Note, <samp>-Wtabs</samp> is +active for <samp>-pedantic</samp>, <samp>-std=f95</samp>, <samp>-std=f2003</samp>, +<samp>-std=f2008</samp>, <samp>-std=f2018</samp> and +<samp>-Wall</samp>. +</p> +<a name="index-Wundefined_002ddo_002dloop"></a> +<a name="index-warnings_002c-undefined-do-loop"></a> +</dd> +<dt><code>-Wundefined-do-loop</code></dt> +<dd><p>Warn if a DO loop with step either 1 or -1 yields an underflow or an overflow +during iteration of an induction variable of the loop. +This option is implied by <samp>-Wall</samp>. +</p> +<a name="index-Wunderflow"></a> +<a name="index-warnings_002c-underflow"></a> +<a name="index-underflow"></a> +</dd> +<dt><code>-Wunderflow</code></dt> +<dd><p>Produce a warning when numerical constant expressions are +encountered, which yield an UNDERFLOW during compilation. Enabled by default. +</p> +<a name="index-Wintrinsic_002dshadow"></a> +<a name="index-warnings_002c-intrinsic"></a> +<a name="index-intrinsic"></a> +</dd> +<dt><code>-Wintrinsic-shadow</code></dt> +<dd><p>Warn if a user-defined procedure or module procedure has the same name as an +intrinsic; in this case, an explicit interface or <code>EXTERNAL</code> or +<code>INTRINSIC</code> declaration might be needed to get calls later resolved to +the desired intrinsic/procedure. This option is implied by <samp>-Wall</samp>. +</p> +<a name="index-Wuse_002dwithout_002donly"></a> +<a name="index-warnings_002c-use-statements"></a> +<a name="index-intrinsic-1"></a> +</dd> +<dt><code>-Wuse-without-only</code></dt> +<dd><p>Warn if a <code>USE</code> statement has no <code>ONLY</code> qualifier and +thus implicitly imports all public entities of the used module. +</p> +<a name="index-Wunused_002ddummy_002dargument"></a> +<a name="index-warnings_002c-unused-dummy-argument"></a> +<a name="index-unused-dummy-argument"></a> +<a name="index-dummy-argument_002c-unused"></a> +</dd> +<dt><code>-Wunused-dummy-argument</code></dt> +<dd><p>Warn about unused dummy arguments. This option is implied by <samp>-Wall</samp>. +</p> +<a name="index-Wunused_002dparameter"></a> +<a name="index-warnings_002c-unused-parameter"></a> +<a name="index-unused-parameter"></a> +</dd> +<dt><code>-Wunused-parameter</code></dt> +<dd><p>Contrary to <code>gcc</code>’s meaning of <samp>-Wunused-parameter</samp>, +<code>gfortran</code>’s implementation of this option does not warn +about unused dummy arguments (see <samp>-Wunused-dummy-argument</samp>), +but about unused <code>PARAMETER</code> values. <samp>-Wunused-parameter</samp> +is implied by <samp>-Wextra</samp> if also <samp>-Wunused</samp> or +<samp>-Wall</samp> is used. +</p> +<a name="index-Walign_002dcommons"></a> +<a name="index-warnings_002c-alignment-of-COMMON-blocks"></a> +<a name="index-alignment-of-COMMON-blocks"></a> +</dd> +<dt><code>-Walign-commons</code></dt> +<dd><p>By default, <code>gfortran</code> warns about any occasion of variables being +padded for proper alignment inside a <code>COMMON</code> block. This warning can be turned +off via <samp>-Wno-align-commons</samp>. See also <samp>-falign-commons</samp>. +</p> +<a name="index-Wfunction_002delimination"></a> +<a name="index-function-elimination"></a> +<a name="index-warnings_002c-function-elimination"></a> +</dd> +<dt><code>-Wfunction-elimination</code></dt> +<dd><p>Warn if any calls to impure functions are eliminated by the optimizations +enabled by the <samp>-ffrontend-optimize</samp> option. +This option is implied by <samp>-Wextra</samp>. +</p> +<a name="index-Wrealloc_002dlhs"></a> +<a name="index-Reallocate-the-LHS-in-assignments_002c-notification"></a> +</dd> +<dt><code>-Wrealloc-lhs</code></dt> +<dd><p>Warn when the compiler might insert code to for allocation or reallocation of +an allocatable array variable of intrinsic type in intrinsic assignments. In +hot loops, the Fortran 2003 reallocation feature may reduce the performance. +If the array is already allocated with the correct shape, consider using a +whole-array array-spec (e.g. <code>(:,:,:)</code>) for the variable on the left-hand +side to prevent the reallocation check. Note that in some cases the warning +is shown, even if the compiler will optimize reallocation checks away. For +instance, when the right-hand side contains the same variable multiplied by +a scalar. See also <samp>-frealloc-lhs</samp>. +</p> +<a name="index-Wrealloc_002dlhs_002dall"></a> +</dd> +<dt><code>-Wrealloc-lhs-all</code></dt> +<dd><p>Warn when the compiler inserts code to for allocation or reallocation of an +allocatable variable; this includes scalars and derived types. +</p> +<a name="index-Wcompare_002dreals"></a> +</dd> +<dt><code>-Wcompare-reals</code></dt> +<dd><p>Warn when comparing real or complex types for equality or inequality. +This option is implied by <samp>-Wextra</samp>. +</p> +<a name="index-Wtargt_002dlifetime"></a> +</dd> +<dt><code>-Wtarget-lifetime</code></dt> +<dd><p>Warn if the pointer in a pointer assignment might be longer than the its +target. This option is implied by <samp>-Wall</samp>. +</p> +<a name="index-Wzerotrip"></a> +</dd> +<dt><code>-Wzerotrip</code></dt> +<dd><p>Warn if a <code>DO</code> loop is known to execute zero times at compile +time. This option is implied by <samp>-Wall</samp>. +</p> +<a name="index-Wdo_002dsubscript"></a> +</dd> +<dt><code>-Wdo-subscript</code></dt> +<dd><p>Warn if an array subscript inside a DO loop could lead to an +out-of-bounds access even if the compiler cannot prove that the +statement is actually executed, in cases like +</p><div class="smallexample"> +<pre class="smallexample"> real a(3) + do i=1,4 + if (condition(i)) then + a(i) = 1.2 + end if + end do +</pre></div> +<p>This option is implied by <samp>-Wextra</samp>. +</p> +<a name="index-Werror"></a> +<a name="index-warnings_002c-to-errors"></a> +</dd> +<dt><code>-Werror</code></dt> +<dd><p>Turns all warnings into errors. +</p></dd> +</dl> + +<p>See <a href="http://gcc.gnu.org/onlinedocs/gcc/Warning-Options.html#Warning-Options">Options to Request or Suppress Errors and +Warnings</a> in <cite>Using the GNU Compiler Collection (GCC)</cite>, for information on +more options offered by the GBE shared by <code>gfortran</code>, <code>gcc</code> +and other GNU compilers. +</p> +<p>Some of these have no effect when compiling programs written in Fortran. +</p> +<hr> +<div class="header"> +<p> +Next: <a href="Debugging-Options.html#Debugging-Options" accesskey="n" rel="next">Debugging Options</a>, Previous: <a href="Preprocessing-Options.html#Preprocessing-Options" accesskey="p" rel="previous">Preprocessing Options</a>, Up: <a href="Invoking-GNU-Fortran.html#Invoking-GNU-Fortran" accesskey="u" rel="up">Invoking GNU Fortran</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> +</div> + + + +</body> +</html> |