The standard default format for error messages is called “brief format”. Brief format messages are written to stderr (the standard error file) and have the following form:
e.adb:3:04: Incorrect spelling of keyword "function" e.adb:4:20: ";" should be "is"
The first integer after the file name is the line number in the file,
and the second integer is the column number within the line.
GPS can parse the error messages
and point to the referenced character.
The following switches provide control over the error message
|3. funcion X (Q : Integer) | >>> Incorrect spelling of keyword "function" 4. return Integer; | >>> ";" should be "is"|
The vertical bar indicates the location of the error, and the ‘>>>’
prefix can be used to search for error messages. When this switch is
used the only source lines output are those with errors.
lstands for list. This switch causes a full listing of the file to be generated. In the case where a body is compiled, the corresponding spec is also listed, along with any subunits. Typical output from compiling a package body p.adb might look like:
|Compiling: p.adb 1. package body p is 2. procedure a; 3. procedure a is separate; 4. begin 5. null | >>> missing ";" 6. end; Compiling: p.ads 1. package p is 2. pragma Elaborate_Body | >>> missing ";" 3. end p; Compiling: p-a.adb 1. separate p | >>> missing "(" 2. procedure a is 3. begin 4. null | >>> missing ";" 5. end;|
When you specify the -gnatv or -gnatl switches and
standard output is redirected, a brief summary is written to
stderr (standard error) giving the number of error messages and
warning messages generated.
bstands for brief. This switch causes GNAT to generate the brief format error messages to stderr (the standard error file) as well as the verbose format message or full listing (which as usual is written to stdout (the standard output file).
mstands for maximum. n is a decimal integer in the range of 1 to 999999 and limits the number of error or warning messages to be generated. For example, using -gnatm2 might yield
e.adb:3:04: Incorrect spelling of keyword "function" e.adb:5:35: missing ".." fatal error: maximum number of errors detected compilation abandoned
The default setting if no switch is given is 9999. If the number of warnings reaches this limit, then a message is output and further warnings are suppressed, but the compilation is continued. If the number of error messages reaches this limit, then a message is output and the compilation is abandoned. A value of zero means that no limit applies.
Note that the equal sign is optional, so the switches
-gnatm2 and -gnatm=2 are equivalent.
fstands for full. Normally, the compiler suppresses error messages that are likely to be redundant. This switch causes all error messages to be generated. In particular, in the case of references to undefined variables. If a given variable is referenced several times, the normal format of messages is
e.adb:7:07: "V" is undefined (more references follow)
where the parenthetical comment warns that there are additional
references to the variable
V. Compiling the same program with the
-gnatf switch yields
e.adb:7:07: "V" is undefined e.adb:8:07: "V" is undefined e.adb:8:12: "V" is undefined e.adb:8:16: "V" is undefined e.adb:9:07: "V" is undefined e.adb:9:12: "V" is undefined
The -gnatf switch also generates additional information for some error messages. Some examples are:
If the -gnatjnn switch is used with a positive value for nn, then
messages are output in a different manner. A message and all its continuation
lines are treated as a unit, and count as only one warning or message in the
statistics totals. Furthermore, the message is reformatted so that no line
is longer than nn characters.
qstands for quit (really “don't quit”). In normal operation mode, the compiler first parses the program and determines if there are any syntax errors. If there are, appropriate error messages are generated and compilation is immediately terminated. This switch tells GNAT to continue with semantic analysis even if syntax errors have been found. This may enable the detection of more errors in a single run. On the other hand, the semantic analyzer is more likely to encounter some internal fatal error when given a syntactically invalid tree.
In addition, if -gnatt is also specified, then the tree file is generated even if there are illegalities. It may be useful in this case to also specify -gnatq to ensure that full semantic processing occurs. The resulting tree file can be processed by ASIS, for the purpose of providing partial information about illegal units, but if the error causes the tree to be badly malformed, then ASIS may crash during the analysis.
When -gnatQ is used and the generated ALI file is marked as being in error, gnatmake will attempt to recompile the source when it finds such an ALI file, including with switch -gnatc.
Note that -gnatQ has no effect if -gnats is specified, since ALI files are never generated if -gnats is set.